AN ABSTRACT OF THE THESIS OF

FLASH GIBSON(Name of Student)

in Zoology

Title:.

(Major)

for the DOCTOR OF PHILOSOPHY(Degree)

presented on May 6, 1971(Date)

BEHAVIORAL PATTERNS AND THEIR TEMPORAL

ORGANIZATION IN BREEDING AMERICAN AVOCETS

Abstract approved:Redacted for privacy

(,John A. Wiens

The organization of behavioral activities in time is important

to a bird's survival and reproduction. To be successful, either

proximately or ultimately, a bird must apportion its behavior in time

so that it may obtain sufficient energy for maintenance activities and

for such activities as migration and reproduction. The organization

of behavioral activities in time can be expressed as a time budget.

I have described the action patterns and displays of breeding American

Avocets (Recurvirostra americana) and have examined the budgeting

of time among these behaviors and its possible adaptiveness. Particu-

lar consideration is given to patterns of seasonal, diurnal and sexual

variations.

The study area was located within an alkaline marsh at Summer

Lake, Oregon. The time budget data were collected by recording at

10 sec. intervals the amount of time spent in 12 categories of behavior.

During the 1969 breeding season (April-July) 422 hrs. of data were

taken on 36 individuals.

The breeding season was divided into four stages ; prenesting,

incubation, parental care and post breeding. Seasonally, all main-

tenance activities combined took 67% of the avocet's time, and repro-

ductive activities took 26%. Of all activities, feeding took the largest

portion of time (36%). Feeding, because of its close relationship to

bioenergetics, is probably one of the most important aspects of the

time budget. Through the breeding season energy requirements

change, and this is reflected in a seasonal flux in time spent feeding.

I suggest that seasonal variation in temperature, activity levels, prey

abundance, and such energetically expensive processes as egg produc-

tion, molting and premigratory fat deposition may determine the

amount of time spent foraging. There was little seasonal fluctuation

in the amount of time spent in resting, preening, or in aggressive

activities. Incubation and caring for the young required similar

amounts of time.

Diurnally, several categories of behavior, such as feeding,

preening and nest building, exhibited morning and afternoon peaks

of activity, separated by a period of inactivity at midmorning.

This pattern held when all "active" action patterns were combined.

I concluded that foraging patterns largely dictate the form of the

diurnal activity pattern. The morning feeding peak may be related

to a need to feed after the night-long fast, while the afternoon peak is

perhaps associated with optimum environmental conditions for feeding,

such as maximum insect availability.

Avocet males and females exhibited few significant differences

in either the seasonal or diurnal time budgets. However, males

appeared to be more aggressive while females spent more time incu-

bating. The general similarities of morphology, behavior, and tem-

poral organization of behavior, indicate that the sexes have similar

roles in the social system, and may be ecologically similar as well.

Behavioral Patterns and Their Temporal Organizationin Breeding American Avocets

by

Flash Gibson

A THESIS

submitted to

Oregon State University

in partial fulfillment ofthe requirements for the

degree of

Doctor of Philosophy

June 19 71

APPROVED:

Redacted for privacy

Associate Profe s r of Zoologyin charge of major

Redacted for privacy

Chairman of the Department of Zoology

Redacted for privacy_VDean diura/ duate School

Date thesis is presented , /77/Typed by Opal Grossnicklaus for Flash Gibson

ACKNOWLEDGEMENTS

Many people have made the completion of this project possible.

I would like to give special thanks to the Oregon State Game Commis-

sion, A. B. Claggett, and W. Olsen for supplying housing for me and

my family and for their valuable council. Dr. R. B. Hamilton gener-

ously supplied me with a copy of his thesis.

I would like to acknowledge Dr. S. G. Martin for helping set up

field equipment and for offering much valuable discussion concerning

the methodology used in this study. Several of my colleagues have

been particularly helpful in their discussions of the theoretical aspects

of this study. In this regard my thanks go to D. Kroodsma, J. States,

M. Scott, and T. Haislip.

My major professor Dr. J. A. Wiens was helpful through all

phases of the study and was invaluable in his supervision of the prepa-

ration of this manuscript. I would like to thank D. Neiss for writing

the computer programs used in the analysis of the data. Special

appreciation goes to Lorna States for her fine drawings of avocet

action patterns. Finally my inexpressable thanks go to my wife,

Linda, wh,, did many of the tedious secretarial duties and offered

continual encouragement. A grant from the Oregon State Computer

Center made analysis of the data possible. Funds for this research

were supplied by a N. D. E. A. Predoctoral Fellowship.

TABLE OF CONTENTS

INTRODUCTION

THE STUDY AREA

1

3

The Summer Lake Management Area 3

Distribution of Water 5

The Vegetation 6

PROCEDURES 8

Constructing the Ethogram 8Breeding Biology 9Marking Individuals 10The Time Budget 11Analysis of the Data 14

BREEDING BIOLOGY 16

Migration and Arrival 16Breeding Chronology 18Territory 21The Nest 25Nest Dispersion 27Egg Laying 29Incubation 3 0Hatching 34Care of the Young 36Preparation for Migration 3 7

THE ETHOGRAM 40

Maintenance Behavior 42Mating Behavior 48Aggressive Behavior 52Diver sionary i3ehavior 59Nesting Behavior 6ZParental Behavior 66Miscellaneous Action Patterns 68

THE TIME BUDGET ANALYSIS69

Behavioral Categories 70The Seasonal Time _budget 72Sexual Differences in the Seasonal Time Budget 79The Diurnal Time Budget 84Sexual Differences in the Diurnal Time Budget 91

DISCUSSION95

Energy and Seasonal Changes in Foraging Activity 96Energy and Seasonal Patterns in Non-feeding Activities 105The Bimodal Nature of the Activity Pattern 106Sexual Aspects of the Time Budget 113

BIBLIOGRAPHY 11 7

APPENDICES

Appendix

1 Seasonal time budget for all action patterns 1 21

2 Diurnal time budget for all action patterns 1 23

3 Seasonal time budget with categories ofbehavior, sexes combined 135

4 Seasonal time budget with categories ofbehavior

5 Diurnal time budget with categories ofbehavior, sexes combined

6 Diurnal time budget with categories ofbe

136

137

139

Calculation of Standard Metabolism 1 43

LIST OF FIGURES

Figure Page

1. The Summer Lake Management Area 4

Z. Habitat features of the Summer Lake ManagementArea 7

3. A portion of the standardized data form 12

4. The diurnal period during which time budget datawere taken. 13

5. The breeding and wintering distribution of theAmerican Avocet 1 7

6. Arrival of migrants at Summer Lake 19

7. Breeding chronology for the avocet population atSummer Lake 20

8. Territories of six pairs of avocets during the incuba-tion period 23

9. Avocet nest dispersion in different habitats atSummer Lake 28

10. Time of nest initiation at Summer Lake in 1968 and1969. 31

11. Avocet action patterns: feeding, flock feeding, preen-ing, resting 43

1 2. Avocet action patterns: bathing, scratching, two-wingstretch, wing-leg stretch 47

13. Avocet action patterns: precopulatory breast preening,mount, crossed bills

50

14. Avocet action patterns: crouch, single crouch-run,paired crouch-run, pursuit attack, retreat 54

15. Avocet action patterns: jump attack, wingspread,bowing, squatting, psuedosleeping 56

FigurePage

16. Avocet action patterns: tightrope, sneak-run, breastdipping, flying 61

17. Avocet action patterns: throwing straws, scraping,groundchecking, nest approach, incubation 65

18. Avocet action patterns: upright, parallel walk,brooding 67

19. The seasonal time budget, sexes combined 73

20. The seasonal time budget for both sexes 81

21. The diurnal time budget, sexes combined 86

22. The diurnal time budget for both sexes 92

23. The seasonal temperature regime for SummerLake during 1969 97

24. Generalized relationships between time spent infeeding by avocets and energy demands 98

25. Seasonal pattern of aquatic insect emergence forthe Whistler's Bend Impoundment, Douglas County,Oregon. 103

26. The apportionment of avocet time to an "active" state 107

27. The diurnal apportionment of time by avocets to 7categories of behavior for the entire breeding season 108

28. The diurnal foraging pattern for avocets; the diurnaltemperature regime; the diurnal pattern of emergenceof Tri.coptera 110

LIST OF TABLES

Table

1. The relationship between nest location and nestlining

Page

26

2. Role of the sexes during the incubation period at 4nests during 1969 33

3. Summary of avocet hatching data for 1969 35

4. Number of chicks in broods of two age classesduring 1969 38

5. Summary of avocet behavior patterns

6. Categories of behavior used in the time budgetanalysis

7. Diurnal incubation pattern for each sex

8. Percent total observation time spent in an "active"state for each stage of the breeding cycle

41

71

85

100

BEHAVIORAL PATTERNS AND THEIR TEMPORALORGANIZATION IN BREEDING

AMERICAN AVOCETS

INTRODUCTION

The time budget of a bird, the way it uses time in the perform-

ance of various activities, is important to survival and reproduction.

To be successful (either proximately,or ultimately), a bird must ap-

portion its time so that it has sufficient energy for metabolic functions

and for activities such as migration and reproduction. The arrange-

ment of the time budget must be closely attuned to environmental

conditions; a bird whose time budget is not properly phased in rela-

tion to environmental conditions will be at a selective disadvantage

(Orians, 1961; Verbeek, 1964; Verner, 1965).

There are two basic types of time budget --annual and diurnal.

Verner (1965) suggests that there is a hypothetical "best" annual and

diurnal time budget for a given set of circumstances and that selec-

tion will favor those individuals whose budgets most closely approach

this optimum. For example, a bird that migrates too early or too

late in the spring and consequently lays eggs too early or too late in

relation to local conditions will probably produce fewer offspring

and thus be at a selective disadvantage. Likewise, diurnal patt,-rns

of behavior are disadvantageous if improperly arranged. Aggressive

neglect is an excellent example of this (Ripley, 1961). An overly

2

aggressive male may spend an excessive portion of his time defend-

ing his territory, thus neglecting courtship and care of the young.

Consequently he produces fewer offspring than his neighbors.

Orians (1961) first emphasized the evolutionary importance of

time budgets and various aspects have been further developed by

other workers (e. g., Verbeek, 1964; Verner, 1965; Morton, 1967;

Smith, 1968; Martin, 1971). Diurnal rhythms of behavior have been

studied for many years with little emphasis on the evolutionary impor-

tance of these rhythms (e.g., Lees, 1948; Palmgren, 1949; Kluyver,

1950; Cullen, 1954; Gibb, 1954, 1956).

The present investigation was undertaken to further develop

the concept that the apportionment of time is an important ecological

and behavioral feature with adaptive significance. The American

Avocet (Recurvirostra americana) was chosen for study partly from

my own interest in the bird and partly because it is large and easily

observed. I have analyzed the avocet's use of time through the bread-

ing cycle with emphasis on seasonal, diurnal and sexual variations.

3

THE STUDY AREA

The study area was located within the Summer Lake Manage-

ment Area, a game refuge administered by the Oregon State Game

Commission (Figure 1). The refuge is located in Lake County,

Oregon (T30S, R16E) at an elevation of 1310 m. The topography

of the area is typical of northern portions of the Great Basin. It is

characterized by north-trending fault-block mountains and basins

with no external drainage (Baldwin, 1964). The Summer Lake Valley

is a graben lying between opposing fault-blocks, one of which is

Winter Rim, rising 940 m above the valley floor. The valley con-

tains a large alkaline lake with a marsh located at its north end. The

majority of the study was carried out in this marsh.

The Summer Lake Management Area

The management area covers approximately 7290 ha. The

Oregon Game Commission has constructed a series of canals and

dikes to regulate water flow in the marsh. Control of water levels

is partially dependent on irrigation practices in other portions of the

valley. Therefore, water levels are not always held at ideal levels.

However, the majority of the water supplying the marsh comes from

the artesian-fed Ana River, thus assuring a fairly constant water

supply even in the driest years.

Figure 1. The Summer Lake Management Area, Lake County,Oregon

17, MARSH

OPEN WATER

GRAVEL ROAD*-CENSUS ROUTE

ANARESERVOIR

4

.111,

..\.111

".

.\\SUMMER LAKE

I mile

5

Two major dikes traverse the marsh. In the eastern portion

there is Bulgate Dike (4 km long) and in the west, Windbreak Dike

(3. 2 km long) (Figure 1). Both dikes range from 20-50 m in width.

The dikes within the marsh are topped by service roads, making much

of the area accessible by automobile. The majority of this study was

conducted in the Windbreak Dike area.

A large portion of the eastern part of the marsh is characterized

by large alkali flats which are mostly devoid of vegetation. The west-

ern side is extensively vegetated.

Distribution of Water

Water in the marsh is distributed in two ways. In the eastern

and northern portions, water is localized in a patchy distribution of

ponds and canals. In contrast, the region around Windbreak Dike,

extending west to Oregon Highway 31, is extensively covered with

shallow water. The Ana River flows into the area west of Windbreak

Dike; it is also supplied by irrigation run-off from agricultural areas

along the west edge of the valley. These two factors account for the

moister conditions in this area.

Water depths in ponds and waterways throughout most of the

marsh range from 1 to 15 cm. However, some of the larger ponds

in the northern part of the marsh are up to 2 m deep.

6

The Vegetation

The vegetation of the entire marsh is dominated by rushes

(Scirpus sp. ) and salt grass (Distichlis stricta). The eastern half

of the marsh is almost devoid of vegetation except for localized

patches,. The vegetation in the vicinity of Windbreak Dike is char-

acterized by salt grass in dry areas, while three-square tule (Scirpus

americanus) and marsh bullrush (S. robustus) occur in wet soils and

shallow water. Great bullrush (S. validus) and cattail (Typha latifolia)

have a patchy distribution in deeper water. Rabbit brush (Chryso-

thamnus nauseosus) and willows (Salix sp. ) occur sparsely along the

dikes (Figure 2).

Figure 2. Habitat features of the Summer Lake ManagementArea. A. The western part of the marsh in thevicinity of Windbreak Dike. B. Typical playa onthe eastern edge of the marsh.

S

I

8

PROCEDURES

Field work was conducted over 271 days during the spring and

summer of 1967 (15 May-10 August), 1968 (7 April-13 July), and

1969 (1 April-10 July).

The quantitative data for the time budget analysis were collected

during the 1969 breeding season only. The 1967 and 1968 seasons

were spent constructing an ethogram, collecting breeding biology

information, and devising methods for quantifying behavioral activi-

ties in time.

Constructing the Ethogram

An ethogram consists of a detailed description of a species'

behavior with particular emphasis on stereotyped and semistereo-

typed action patterns. This phase of the study was necessary be-

cause of the lack of adequate descriptive accounts of avocet behavior

in the literature. A few sketchy observations were given in Bent

(1927), and an ethogram of the European Avocet (Recurvirostra

avocetta) was pllblished by Makkink in 1936. The relevance of

Makkink's work to the behavior of the American species could not

be determined until observations on the latter were completed.

It is essential in any study of the apportionment of time to

various activities that all activities be precisely described and

9

categorized. Behavioral observations were made principally from

an automobile or from 3.3 m towers. Observations were either taken

directly as field notes or dictated into a portable tape recorder and

then transcribed into notebooks. Observations were aided by the

use of 7 X50 binoculars, a 20 X spotting scope, and cine and still

photography.

Breeding Biology

Information on breeding biology, like the basic behavioral de-

scriptions, was inadequate prior to this study. Therefore basic life

history data were obtained using the following methods.

I located all nests along Windbreak dike in 1967 and 1969, while

only selected nests were studied in 1968. Eggs were marked with

fingernail polish and their fate followed by twice daily checks during

egg laying and hatching, and alternate day checks during incubation.

Time budget data were used to obtain estimates of the roles of the

sexes in such activities as incubation and parental care.

In order to assess the flux of breeding activities for a larger

segment of the Summer Lake population, a 3.75 km census route

was established (Figure 1), along which all avocets were counted

and their activity recorded. This gave an index to the number of

birds in each stage of the breeding cycle, since particular action

patterns are characteristic of certain breeding stages.

10

To determine the position, boundaries, and patterns of utiliza-

tion of avocet territories, I recorded the position of both members

of a pair within a 15.2 X 15.2 m grid system at 10 sec. intervals.

Observations were collected and mapped to provide information on

flux of territory size and utilization patterns.

Marking Individuals

Individually marked birds were essential to the study so that

individuals could be followed for long periods of time and their breed-

ing schedules monitored. A large number of marking methods were

tried, but most proved unsuccessful. Dyeing adults with dyes such

as Nyazol A (black), picric acid (yellow), rhodamine B (red) and

methyl green (blue) did, however, prove successful. The dye was

applied by placing a piece of cellulose sponge one inch square in the

nest with a nail. The sponge was soaked with dye and when the bird

returned to the nest a large splotch of color was transferred to 5+3

breast. The yellow color of picric acid presented a problem, how-

ever. When an incubating bird found the yellow object in its nest,

it immediately deserted. This may have involved a reaction similar

to that evoked when a bird discovers a nest full of broken eggs with

yolk showing. The problem was averted by mixing a little methyl

green with the picric acid, resulting in a green dye. A day or two

11

after application the green color was gone, leaving yellow. All

dyes except methyl green lasted at least a month.

The Time Budget

A total of 422 hours of time budget data was recorded for 36

different avocets (213 hours on males and 209 hours on females). The

time spent in 40 different categories of behavior (see Ethogram) wereused in the time budget. A system of shorthand symbols was devel-oped so that action patterns could be rapidly recorded on a standard-ized data form (Figure 3). The activities of both members of a pairwere recorded simultaneously at 10 sec. intervals for a 30 min.

observation period. The time base was kept with a periodic metro-

nome timing device (Wiens et al., 1970) which was set to pulse every10 sec.

Time budgets were taken systematically from 0600 to 1800 sothat the 12 hr. period was sampled every three days. Sampling the

same 12 hr. period through the breeding season had its drawbacks,

since there were periods of daylight before and after the interval of

observation (Figure 4). Further, the period sampled changed in

relation to sunrise and sunset as the season progressed. This made

the diurnal time budgets somewhat incomplete, but since I examined

mainly general patterns of time utilization, this incompleteness

should not mask overall patterns.

Figure 3. A portion of a standardized data form on whichtime budget information was taken. A completedata sheet was used to record the action patterns(A. P.) of both males and females for 30 min. Ateach 10 sec. interval the action pattern of each sexwas recorded using shorthand symbols. If therewas no change a slash was marked through theinterval. F = feeding; SCR = scratching; Fl =flying; R = resting; P = preening; Ba = bathing;WS = wingshake.

DATE 5114/ " TIME Coo-630STAGE

LOCATION Winlbrca < TERRITORY NO. NEST NO. Cl ear 4o laiWEATHER

10 SEC. INTERVAL

360 SEC. PER LINE N.)

Figure 4. The diurnal period during which behavioralobservations were made. Observations wereinitiated at 0600 (A) and terminated at 1800 (B).The entire daylight period was not sampled.

APRILJUNE 4 JULY

600

800

10 00

12 00

shift to daylight savings time

14 00

16 00

sunset1800

APRIL 1 MAY JUNE 1 JULY

sunrise

6 00

800

to 00

12 00

14 00

1600

14

Eighteen avocet pairs were observed during the season, but

only four pairs were followed through a breeding cycle. The length

of the breeding cycle (60-70 days) for a single pair prevented inten-

sive study of additional pairs. The selection of pairs for observation

was done as systematically as possible to avoid the problems of oppor-

tunistic observations (Wiens et al., 1970). The pairs being used for

collecting time budget data were numbered sequentially and observed

on a rotating basis.

Analysis of the Data

The time budget data were compiled and analyzed on the CDC

3300 operated by the Oregon State Computer Center. The raw data

were coded and punched onto computer cards. A total of 12,000

cards was necessary to handle the 422 hours of data. Computer

analysis was essential because of the difficulty of calculating the

time utilization of 40 action patterns for two sexes for four breeding

cycle stages and for six diurnal time periods within each stage; a

nearly impossible task by hand.

Since I wished to express the time budget in terms of the per-

cent of the total time spent in each activity, the computer output in-

cluded these analyses. But this presented a problem of applying

statistical methods to percentages. Due to lack of funds the data

could not be reanalyzed in such a way so that standard statistical

15

methods could be applied. Therefore, to generate confidence inter-vals an approximation to the binomial was performed on each per-

centage (Huntsberger, 1967). This is valid since percentages are

ratios based on 100 percent. The drawback to this method is thatthe confidence interval generated is strongly dependent on samplesize. Therefore, I had to decide on a unit of time to use for the

analysis. My decision was to use minutes since I felt that this unithad some biological meaning. In other words, I felt minute to minute

changes in activities were more meaningful in the time budget than

second to second or hour to hour changes for many activities. This

selection is obviously a compromise but I feel it is the best of those

available. More specific information about certain analytical pro-

cedures will be covered in each section as they are used.

16

BREEDING BIOLOGY

The American Avocet is a fairly large wader, 39 to 52 cm in

length. In the breeding plumage the avocet has a rust-colored head

and neck with a bold black and white pattern on its back. A major

characteristic is its recurved bill. There is some sexual dimorphism,

in that the female always has a more strongly recurved bill than the

male (Hamilton, 1969 ).

The American Avocet breeds in western North America and

winters along the Pacific coast from San Francisco to Central

America and inland across the southwest United States and northern

Mexico (Figure 5) (Hamilton, 1969). The preferred breeding habitat

is shallow alkaline or saline marshes and lakes. Nesting sites are

usually in open areas with sparse vegetation such as low grass

covered islands, shores or mudflats.

Migration and Arrival

Avocets have both migratory and non-migratory populations.

All populations in Oregon are migratory. Paths of migration and

the respective wintering areas of specific populations are unknown.

Summer Lake supports one of the largest breeding populations in

Oregon.

During my observations, spring migrants began arriving at

Figure 5. The breeding and wintering distribution of theAmerican Avocet (from Hamilton, 1969).

11111111

17

BREEDING RANGE

WINTER RANGE

0

0 400 800 1200

scale of miles

18

Summer Lake around 20-25 March and most had arrived by the end

of April (Figure 6). The greatest influx of birds occurred between

1-15 April. In early April single birds and small flocks of four to

ten were frequently observed. Whether the birds migrate in flocks

or as individuals, at night or during the day, is unclear. Hamilton

(pers. comm.) suggests that they migrate at night since he found

that in certain wintering areas in south San Francisco Bay there

were fewer and fewer birds each day until all birds had gone.

At the peak of migration in mid-April large flocks of avocets

were present in the larger bodies of water within the marsh. The

number of birds varied considerably from day to day, suggesting

that Summer Lake was a stopping-over spot for many avocets con-

tinuing on to other areas.

Breeding Chronology

Avocet breeding activities extended over a four-month perin-2

from late March until late July. Figure 7 summarizes the breeding

chronology for avocets at Summer Lake during the 1969 season.

I have divided the breeding cycle into four stages:

Stage 1: Preresting includes all activities up to the laying of

the first egg. For any single pair, territory establishment, court-

ship, nest site selection, and nest building activities occurred during

the same time period and therefore could not be separated into

Figure 6. An index to avocet population numbers in theSummer Lake Management Area during the 19 69breeding season.

zL1J

250

200

150

100

APRILMAY

TEN DAY INTERVALSJUNE

Figure 7. A. A breeding chronology for the avocet populationat Summer Lake during the 1969 breeding season.B. A breeding chronology for a single pair. Thebeginning and end of each stage are based on dateswhen various breeding activities were first and lastobserved.

A

I

arrival

H

IMO alb WIZ 7.1M.

territorial establishment

courtship

nest building

1

egg laying

incubation,a,

20

hatching

15 15 15april may June

DATE

egglaying hatching

Incubation

24 days

5 days

rearing theyoung

25-35 days

15

July

post season flocking and migration

2 days

21

stages (Figure 7B). For the majority of the population this stage

lasted from arrival until around May 1st.

Stage 2: Incubation began with the laying of the first egg and

continued until the last egg hatched. The incubation stage was ex-

tended through laying and hatching because avocets sat on the eggs

during both of these periods and it was difficult from behavioral

observations to make a distinction. This stage lasted from about

1 May to approximately 15 June.

Stage 3: Parental Care began when the chicks hatched and

continued until the young were fledged. Precise information about

the duration of this stage is lacking because of the difficulty of observ-

ing family groups. Parental care continued from late May until ap-

proximately 15 July.

Stage 4: Post-breeding Flocking began after breeding ceased

for a particular pair. Usually by late June and Early July a sufficient

portion of the population had completed breeding activities to allow

the formation of flocks. Some avocets remained at Summer Lake un-

til October or November.

Territory

Avocets at Summer Lake established and maintained territories

which were defended by both sexes. Territories assumed three

different forms coinciding with the pre-nesting stage, the incubation

22

stage, and the parental stage. Prior to egg laying territories were

centered around feeding areas. Suitable nest sites were generally

available within a few hundred meters of the feeding areas. On my

main study area the feeding and nest sites were in close proximity.

However, on the east side of the marsh where open water was much

more localized, nest sites were not always near the feeding area.

During incubation the form and manner of defense of the terri-

tory changed since it was necessary for one member of the pair to

be present at the nest most of the time. At the Windbreak Dike study

area, where nest sites were surrounded by the feeding areas, a

secondary feeding site was usually established 50 to 130 m from the

nest (Figure 8), usually in a large pond. This secondary foraging

area was also defended against other avocets. The task of defending

two separate areas restricted the effectiveness of territorial defense,

with the result that violations of both territorial spaces by other birds

did occur. Avocets only defended the area on which they were pres-

ent; incubating birds, however, did not leave the nest to defend the

territory. Therefore only one area could be defended at any time,

and intrusions by other birds in the absence of the territory owners

were frequent.

The situation was slightly different at sites where the nest

was located away from the feeding area (Figure 8B). Here only one

foraging site was maintained and there seemed to be only a small

Figure 8. A. Territories of three pairs during the incubationperiod along Windbreak Dike. Each pair defendedtwo territories one which included the nest and asecond in a large pond nearby. B. Territories ofthree pairs located on the eastern edge of theSummer Lake Management Area. The nests wer elocated in an alkali flat some distance from thedefended feeding area resulting in only one foragingsite being defended.

23

24

territory associated with the nest site. The feeding territory was

more exclusive in this case because one member of the pair was

usually in attendance.

Once the eggs hatched the territory became chick-centered

and somewhat mobile. The adults usually moved the chicks to a

suitable foraging site, maintaining a strict territory of roughly 50-

100 m in diameter around them at all times. Defense was inter-

specific as well as intraspecific. Nearly all avian species were

excluded with attacks being most frequent on blackbirds (Icteridae)

and ducks (Anatidae).

Lack (1968) considers members of the family Recurvirostridae

to be monogamous. However, there was not complete fidelity between

members of a pair at Summer Lake. In 1969 I observed three males

and one female (all marked) copulate with birds other than their

mates. These opportunistic copulations always occurred during

the incubation period on the territory of the marked birds. The

breeding condition of the unmarked avocets could not be determined

with accuracy, but in one case a female was followed for several

minutes after a copulation. She intruded other territories and was

driven off, indicating that she might be unpaired. Perhaps the avocet

resembles the oystercatcher (Haematopus ostralegas) in its tendency

to mate with birds outside the pair bond (Makkink, 1942).

Observations on a pair of colorbanded birds in 1967 suggest that

25

pair bonds may last for more than one season. This pair was seen

with young in 1968 but was absent from the study area in 1969. They

were observed together again in May, 1970. Whether they remained

together for the entire year is unknown.

The Nest

Numerous accounts of avocet nest construction have been pub-

lished (Wetmore, 1925; Bent, 1927; Wolfe, 1931; Wheeler, 1955;

Hamilton, 1969). In summary, the nest is a simple scape 15-25 cm

in diameter and 0.5 to 3 cm deep, lined with a variety of materials

from grass to mud chips. The amount of lining is variable; some

nests contain none while others are built up to 38 cm in height

(Wetmore, 1925) in areas subjected to flooding. The largest nest

I found was 7.5 cm high. I sampled 56 nests in order to determine

the materials most commonly used in nest construction and the vege-

tation predominating in the area immediately about the nest (Table I ).

There was a correlation between nest lining and the vegetational sur-

roundings, suggesting that the nest materials were gathered in the

immediate vicinity of the nest. Indeed, behavioral observations

substantiated this view (see Ethogram). The maximum distance

traveled from the nest to obtain materials was only 2-3 m. From

Table 1 it appears that the avocets nesting on Windbreak Dike pre-

ferred salt grass to all other types of vegetation for nesting sites.

Table 1. The relationship between nest location and nest lining as determined by recording thevegetation times present in onE square meter around each nest.

Vegetation Type Number of nests lined Number of nests locatedwith vegetation type in vegetation type

Distichlis stricta 28 29

Scirpus americanus 5 2

Scirpus sp. 2 1

Kochia scoparia 8 4

Mixture of above 11 6specie s

None 2 14

Total Nests 56 56

27However, in other areas of the refuge avocets nested in other situa-tions as well, including alkali flats devoid of vegetation.

Nest Dispersion

Lack (1968) states that Recurvirostrids nest in loose coloniesand Hamilton (1969) makes a similar statement specifically forR. americana. Loose colonies are generally located on sites whichare more accessible than those of more colonial species, but thenests within the colony are dispersed to aid concealment. Speciesnesting in loose colonies usually do not defend the colony as a group,unlike more colonial birds such as gulls. Therefore, the advantageof a loose colony probably stems from some factor other than safetyfrom predators, presumably feeding behavior (Lack, 1968, p. 140).

Avocets at Summer Lake tended to nest in groups of varyingdensity (Figure 9). Nesting groups were located near foraging areas,suggesting that proximity to suitable feeding sites is an importantfactor in the placement of nests. Hamilton (1969) found that avocetsin his study area also chose nesting sites on dikes which were closestto foraging areas.

The social factors operating in the formation of avocet nestinggroups are unclear. Counter to Lack's (1968) generalization, reac-tion to predators by avocets seems to be an important group activity.When an avian predator, such as a hawk or gull, flew over a nesting

Figure 9. Avocet nest dispersion in different habitats atSummer Lake. A-B. The dispersion of nestsat the same site in 1969 and 19 70 respectively.The area is a salt grass habitat located alongWindbreak Dike. The mean distance betweennests in A was 47. 3 m and in B 29.8 m. C. Nestdistribution in a large salt grass field. The meandistance between nests was 80. 0 m. D. Nestdispersion in an alkali flat where themean distancebetween nests was 50 mo E. Nest distribution onand near Windbreak Dike in 1967 and 1969.

El water

nestsaA

~50M a

C

50

50w

s

1989 1967windbreak dike

28

29

area the avocets responded with loud vocalizations and mobbing.

Many avocets chased and dove at the bird. This form of attack was

quite successful in keeping hawks and gulls away from nesting sites.

Avocets responded to terrestrial predators differently. When a hu-

man approached a nesting group most of the birds began calling and

flew to a spot nearby but away from the nests. The entire group

then began giving distraction displays (Hamilton, 1969). I witnessed

up to 35 birds taking part in this activity at a time. I have seen a

deer and coyote effectively distracted by this activity.

Egg Laying

Bent (1927) and Hamilton (1969) state that avocets normally

have a clutch of four eggs. I found a mean clutch size for 111 nests

o 3. 7 (2-4). Nests containing six or more eggs were not included

in the clutch size calculations, as they probably did not represent

the clutch of a single female. Length and width measurements of

eggs in 50 clutches revealed that the eggs of a single female were

uniform in size. Nests containing six or more eggs had two distinct

size classes, suggesting that two females laid the eggs. Dump nest-

ing in this species requires a violation of territory; unfortunately the

mechanism by which this was accomplished was not observed.

The earliest complete clutches were found in late April or early

May. In 1967 and 1968 the first clutch was found on 7 May and in

30

1969 on 24 April. Egg laying reached its peak between 1 1 and 20 May

in 1968 and 1969 (Figure 10).

The laying period for a clutch of four eggs was usually five

days. The interval between eggs was approximately 24-30 hours.

Nests were checked daily between 0800 and 1600. New eggs were

found at the morning check but not in the afternoon, indicating that

eggs were laid in the 16 hour interval between 1600 and 0800.

Data from three nests deserted due to human disturbance

showed that avocets can renest a short time after losing a clutch.

One pair copulated and initiated nest construction one day after de-

sertion. Two pairs completed second clutches of four eggs in eight

days and a third pair took six days (3 eggs). Each pair had less than

four days remaining in the incubation period when they deserted, so

the effect of the stage of incubation on the rapidity of renesting could

not be determined.

Incubation

Both sexes developed incubation patches and incubated, reliev-

ing each other at the nest rather often. From 480 minutes of obser-

vation at each of the three nests, I found that the female's incubation

intervals averaged 52.2 minutes (3 to 255), while the male's aver-

aged 38.0 minutes (3 to 75). Hamilton (1969) reported that males

incubated 87.6 minutes (N=26 intervals) and females 64.3 (N=18

Figure 10. Time of nest initiation at Summer Lake in 1968and 1969. Nest initiation was defined by thelaying of the first egg.

196c3

1969

04

'Z.

21-31

IES DP( It411.1VPA.5

32

intervals). Both estimates are based on small samples and the

large ranges involved indicate that there is considerable variation.

Time budgets of four pairs were analyzed to determine the

amount of time each sex spent on the nest throughout the incubation

period (Table 2). During the first eight days the male spent nearly

twice as much time on the nest as the female. However, these first

eight days were characterized by a high degree of nest inattentive-

ness. The female predominated during the last 16 days of incuba-

tion. Hamilton (1969) found that the male incubated about twice as

much as the female but he gives no indication at which stage of the

incubation period he collected his data.

The incubation period, defined as the interval from laying of

the last egg until that egg hatches, was 24.2 (22-29) days for 28

nests. Effective incubation probably did not begin until the last egg

was laid because all the eggs generally hatched within a day or two.

However, avocets often covered incomplete clutches during especially

cold or hot weather.

As the season progressed the length of the incubation period

tended to decrease. Nests started in late April averaged 27 days of

incubation; by early May the period had dropped to 25; by mid May

to 24; and finally to 23 in early June. The increase in daytime tem-

peratures as the season progressed may have allowed development

to continue even when the eggs were unattended.

Table 2. Role of the sexes during the incubation period at four nests during the 1969 season

Early (days 1-8) Middle (days 9-16) Late (days 17-24)percent

incubationinattentive N

min.percent

incubationinattentive

min.percentincubation

inattentive N

min.

cf +? d cf+? d cf+Ynest 1 37.8 62.2 00.0 90 42.5 55.8 1.7 360 38.7 58.7 2.7 300

nest 2 63.3 22.2 14.4 180 44,8 54.8 0.4 270

nest 3 41.5 4.6 53.9 390 33.3 59.8 6.8 570 25.9 65.5 8.6 510

nest 4 58.9 27.4 13.7 540 6.1 93.9 0.6 180 55.4 41.1 3.5 720

MEAN 52.3 21.8 25.8 1200 34.4 62.2 3.4 1380 42.3 52.7 5.0 1530

34

Avocets will incubate long past the normal incubation period

if the eggs do not hatch. One pair attended a nest for 39 days before

it was destroyed.

Hatching

Hatching usually occurred over a one or two day period. The

chicks began to pip the eggs four or five days before hatching; they

could be heard calling in the eggs at this time. Shortly before hatch-

ing, a 4-15 mm hole was pipped in the egg. As soon as a chick

freed itself from the egg, a parent removed the shell, dropping it

from 5 to 50 m from the nest. The nidifugous young were usually

dry and able to leave the nest within an hour or two. However the

chicks tended to stay in the nest or near it for at least a day if not

disturbed.

Hatching dates for 78 nests followed during the 1968 and 1969

seasons are summarized in Table 3. Hatching success is similar

to that of other Charadrii (66-96 percent) (Boyd, 1962). Nest losses

due to predation were low; two nests were destroyed by a badger

(Taxidea taxus ); there was no evidence that avian predators de-

stroyed any nests. This may have been a result of the mobbing

behavior of the birds.

Table 3. Summary of avocet hatching data for the 1969 breeding season

No. of Eggsin a Clutch

No.Nests

NoEggs

EggsHatched

Percent ofEggs Hatched

Eggs Hatchedper Nest

2 7 14 6 43 1.1

3 6 18 16 89 2.6

4 59 236 212 90 3.6

7 2 14

8 4 32 3 9 .75

TOTALS 78 314 23 7 79 3.0

36

Care of the Young

Avocets are attentive parents even though they do not feed their

young. Once the chicks hatched, the parents became aggressive

toward all other species including other avocets.

Hamilton (1969) describes broods which contained two age

classes of chicks. He explains the occurrence of mixed broods by

suggesting that avocets are unable to recognize their own young and

lack territoriality during the parental stage. I observed no mixed

broods at Summer Lake. The mixing of broods would require an

intrusion of territorial boundaries. However in certain situations,

when cover is lacking, a disturbance such as an approaching human

creates chaos, with chicks running in all directions. It seems pos-

sible that under such conditions broods could become mixed.

The young spent most of their time feeding and resting. They

exhibited preening and bathing behavior when less than a week old.

Chicks usually ran for cover and lay flat when approached, making

them very difficult to find (Hamilton, 1969). Hiding behavior lasted

until at least the third week, after which they would just run. Chicks

attempted to dive if chased in the water.

When young avocets became separated from their parents they

were often attacked by other avocets. In one instance, in an open

expanse of shallow water, a lone chick was attacked numerous times

37

by four different adults. The young bird was either struck by the

attacker's feet or picked up in the bill and violently shaken. Hamilton

(1969) also reports this activity, as does Makkink (1936) for R .

avocetta.

Parental care continued until after the chicks could fly (four

to five weeks). The members of one brood were able to fly in 27

days. Parental attentiveness waned as the young matured and the

parents spent less time defending the area around them. The actual

duration of the family group is unknown.

In order to determine how successful avocets were in raising

young once they left the nest, I counted the number of young per

brood for two different age classes, those in downy plumage (one to

two weeks of age) and those in juvenile plumage (three to four weeks

old). Weekly counts were made for three weeks during peak hatching

and rearing periods (Table 4). There was no difference between the

number of chicks in the two age classes of broods, each having ap-

proximately three. This indicated that those pairs which hatch young

and do not lose the entire brood are quite successful in raising young,

at least through the first month following hatching.

Preparation for Migration

Once the young could fly the birds joined a post-breeding flock.

This usually involved moving to some of the larger bodies of water

Table 4. Number of chicks in broods of two age classesduring the 1969 breeding season

Age Class No of No. of Chicks/Broods Chicks Brood

Downy Plumage 36 111 3.08

Juvenile Plumage 36 110 3.05

39

within the marsh or to the lake. Flocks began forming in late June

and by mid-July thousands of avocets were congregated along the

west shore of the main lake. The large numbers of birds observed

could not all have come from the marsh. Summer Lake thus seemed

to be a stopping place for migrating avocets, as large numbers could

be seen there in September and even into October (A. B. Claggett,

pers. comm.). The postnuptial molt took place while the birds were

in these flocks.

40

THE ETHOGRAM

Detailed knowledge of a species' behavior is necessary when

studying relationships between its behavior and ecology. An account

of a species' behavioral patterns is classically called an ethogram.

The emphasis in this ethogram will be on descriptions of action pat-

terns and displays characteristic of avocets during the breeding sea-

son. Each phase of behavior will be described, and its overall con-

text and functions given. Many of the action patterns have been previ-

ously described by Hamilton (1969). I have attempted in most cases

to comply with his terminology. The importance of behavioral activi-

ties to this study necessitates that all action patterns used be precisely

described and classified. The separation of behavioral patterns into

discrete units is somewhat subjective. Beginnings and endings of

certain action patterns are indistinct and therefore boundaries must

be established by definition. Precise descriptions make rapid record-

ing of behavioral events in time possible and less subject to error.

Undoubtedly some distortions may occur due to this procedure, but

it is unlikely that it would make a significant difference in the inter-

pretation of the time budgets. For convenience, the avocet's behav-

ioral activities have been divided into broadly functional groupings,

for example maintenance or intraspecific aggressive activities

(Table 5).

Table 5. Summary of avocet behavior patterns

Maintenance BehaviorFeedingFlock feedingFormation FeedingRestingBathingPreeningScratchingTwo-wing StretchWing-leg stretchWings hakeDrinkingFlying

Mating BehaviorPrecopulatory breast preeningNeck ext endedMountCrossed BillsPostcopulatory walk

Aggressive BehaviorIntraspecific aggression

CrouchSingle crouch -runPaired cr ouch -runRetreatPursuit attackBowingJump attackSquatPsuedosleepingParallel walk

Interspecific aggressionPredator chaseDiveWingspread

Diversionary BehaviorTightropeSneak-runBreast dippingAlarm circlingAlarm calling

Nesting BehaviorGround checkingThrowing strawsScrapingNest approachIncubation

Parental BehaviorBroodingLeading

Miscellaneous Action PatternsUprightHead bobbingAbsent

41

42

Maintenance Behavior

Maintenance activities can be considered those behaviors"concerned with locomotion and the general health and efficiencyof the body" (Mar ler, 1956). Maintenance behavior occurs through-out the year.

Feeding (Fig. 11A): Avocets fed in shallow alkaline or salinewater (Hamilton, 1969). Two basic patterns of feeding were em-ployed: "sweep-feeding, " which seems to be essentially tactile innature, and visual feeding. In "sweep-feeding" the recurved billwas swept back and forth across the bottom of the water. The body

was kept at about a 30 ° angle but this varied somewhat according tothe depth of the water. When a food item was captured the head andneck were raised from the water and it was swallowed. Avocets feed-ing in this manner did not hesitate to swim if the water became too

deep for wading. In visual feeding, individuals simply walked slowlyand captured prey items by pecking. This type of feeding usuallyoccurred in summer when large numbers of insects were availablein the marsh. Hamilton (1969) describes nine different feeding meth-ods used by avocets, all of which are modifications of these two basicpatterns. For the present study no separation of feeding methods wasmade.

The above mentioned basic feeding patterns were normally

Figure 11. A. Feeding: Here the sweep-feedingmotion is being used.

B. Flock Feeding: The birds are in a compact

feeding flock, each bird feeding by up-ending.

C. Preening: This bird is rubbing its head

over the uropyial gland.

D. Resting.

A

C

B

D

43

44

employed by solitary individuals and pairs, but in certain social

contexts modifications of these patterns occurred. The first, flock

feeding (Figure 11B), was associated with migratory flocks as they

arrived on the breeding grounds. Large aggregations of avocets

occurred in ponds at Summer Lake in April of each year. These

birds often formed feeding flocks of up to several hundred individuals,

although flocks of 10 to 50 were more common. The birds fed close

together (5-10 cm) and the entire flock moved rapidly through the

water as a unit. The water was usually too deep in these ponds for

wading so the whole group swam. Each bird fed by up-ending, much

as ducks do, and rapidly sweeping the bill back and forth in the wa-

ter. The position of the bill and use of the mandibles was quite differ-

ent from that of birds feeding alone. Flock feeding birds held the

bill open and kept it almost vertical. Avocets feeding in this man-

ner were able to catch small fish (Gibson, in prep. ).

Avocets also fed in groups when they were flocked prior to fall

migration. In formation feeding the form of the feeding groups was

considerably different from those of arriving birds. Three to fifty

birds spaced from 30 to 90 cm apart fed in drill-like formation with

all birds parallel to each other and changing directions as a group.

Formation feeding was most often observed along the shores of

Summer Lake in July and August. The formations wer e usually

rather transitory with birds joining and leaving almost continuously.

45

A particular feeding group would only last from one to ten minutes.

The feeding posture of the birds was similar to that of a solitary bird.

Preening (Fig. 11C): Care of the body surface, particularly the

feathers, was accomplished by preening. The feathers were manipu-

lated with the bill. The wings were preened from the lower side by

drawing each feather between the mandibles. The breast and sides

were preened by a chopping action of the mandibles. Oil was ob-

tained from the uropygial gland and spread on the feathers as de-

scribed above; the head was preened by rolling it back on the uro-

pygial gland and then rubbing it over the back. Water was often used

for preening, with the bill being dipped in the water many times dur-

ing a bout.

Resting (Fig. 11D): Resting avocets usually stood on one leg

with the other leg pulled into the plumage of the breast. The head

was turned backward and the bill was placed under the upper edge

of the wing near the center of the back, or at times the head was

merely pulled in close to the body with the bill pointing straight

forward. The birds sometimes rested on both legs, especially dur-

ing strong winds. Resting birds always faced the prevailing wind.

Scratching (Figure 12B): Scratching was used to manipulate

the feathers on the head. Avocets utilized an indirect or over the

wing scratch. One wing was lowered and extended and a leg was

lifted over the wing to scratch at the head and neck. The neck and

46

head were turned toward the scratching foot. Scratching was of

short duration and occurred at any time

Two-wing Stretch (Figure 12C): The two-wing stretch consist-

ed of raising the wings high over the back until they almost touched.

Simultaneously the neck was extended forward so that it had a some-

what downward arch. The function of stretching according to Sauer

and Sauer (1967) is to reactivate the respiratory center after a period

of rest. This type of stretch also occurred just prior to flight and

when the birds were disturbed (Hamilton, 1969).

Wing and Leg Stretch (Figure 12D): Avocets performing the

wing and leg stretch extended one leg backward at about 80 ° angle

and the wing on the same side was extended down beside the leg.

The primaries of the extended wing were fanned out to some extent.

Bathing (Figure 12A), Bathing occurred in shallow water where

the avocet crouched so that the breast was immersed. The wings

were held loosely at the bird's side and it rocked back and forth_

thrusting its head under the water and then raising it, causing water

to roll over its back. This movement was repeated rapidly over and

over. The wings were often rapidly splashed in the water. The wing

beating was usually interspersed with rocking. Sometimes at the

end of a bout of bathing a bird would dive under the water and propel

itself for a meter or two with its wings. Bathing was almost always

culminated with a violent wing shake and a bout of preening.

Figure 12. A. Bathing: This bird is rocking up and down tocascade water over its back.B. Scratching: The leg is placed over the wing.C. Two -win Stretch.D. Wing-leg Stretch

(t

B

A

4D

C

47

48Drinking: When avocets drank they lowered the bill into the

water, keeping it horizontal to the surface. This caused a curve in

the neck as the avocet leaned forward. After the bill was in the

water the avocet raised it, keeping it horizontal to the water's

surface until the bill could be tipped slightly upward and the water

swallowed.

Wingshake: A wingshake consisted of a rapid beating of the

wings while the bird was standing. The wingshaking often caused the

avocets to rise off the ground slightly and sometimes to hop around

to keep their balance. Wingshaking usually occurred immediately

after bathing or following preening. It was most often observed dur-

ing the post-nuptial molt, possibly in an attempt to dislodge loose

feathers.

Flying (Figure 16D): Avocets were strong and able fliers. In

flight the head and neck were extended anteriorly and the feet and

legs were extended posteriorly. Wing beats were rapid and continu-

ous during flight. They never glided except when landing. At the

end of the descending glide they made a short swoop which killed

their air speed and they dropped softly into the water or onto the

ground.

lya;ting Behavior

Avocet courtship was restricted to a sequence of stereotyped

action patterns which immediately preceded copulation. Neither sex

49

seemed to have a dominant role during sexual encounters since

either the male or female initiated the precopulatory sequence.

The male usually began a courtship sequence by preening at

his breast in a stylized manner (precopulatory breast preening;

Figure 13A). He stood fairly erect and preened at his breast with

rapid chopping motions of the mandibles, frequently dipping his bill

in the water. The male sometimes started this display without appar-

ent stimulation from the female, but more often the female initiated

the precopulatory sequence by assuming the neck extended (Figure

13A) position. She began by breast preening similar to the male

but each time she dipped her bill in the water it was extended further

and further forward until she finally assumed a horizontal position

with neck extended and parallel to the surface of the water. The

angle of the body was dependent upon the depth of the water in which

she was standing. As soon as she was in the neck extended position

the male moved to her side and began or continued precopulatory

breast preening. The male moved in a semicircle from one side of

the female to the other many times by walking behind her. As he

did this he dipped his bill in the water repeatedly. The female would

pivot, maintaining a proper orientation to the male. As the bout

progressed the male's preening became more and more intense.

He shook his bill in the water with increasing violence, spraying

water in all directions. At this point his side feathers were raised

Figure 13, A. Precopulatory Breast Preening: The malestands beside the female preening his breast.B. Mount: Front view; the feathers on the male'ssides are raised.Co Mount: Side view; showing the position of themale on the female's back.D. Crossed Bills: The bills are crossed and themale's wing is extended over the female's back.

A

B

50

51

and he mounted the female (Figure 13B and C) by jumping onto her

back. His feet were placed at the level of the anterior position of

her resting wing. His wings were held extended high over his back.

The male began to lower himself toward the female's cloaca immedi-

ately after mounting. Both held their tail feathers to the side just

before copulation took place. When the male mounted, the female

usually raised her neck out of the water and began to swing back and

forth. The male stayed mounted from five to ten seconds. Immedi-

ately following copulation the male dismounted. As he did, he placed

the wing next to the female over her back and they crossed their bills

(crossed bills; Figure 13D) and performed a pirouette. They then

ran a few steps in this position and parted, each walking a few more

steps with their bills held close to the breast (postcopulatory walk).

Copulations took place all through the prenesting period and

continued for a few days after incubation began. Many species have

displays for attracting mates and to aid the pairing process. Avocets

apparently lack displays of this type. Pairing probably occurred on

the wintering grounds or during migration prior to arrival at Summer

Lake. Pairing on the wintering ground appears to be a simple associ-

ation process in which females associate themselves with males and

persist until they are no longer rebuffed (Hamilton, 1969).

52

Aggressive Behavior

Avocets engaged in both intraspecific and interspecific aggres-

sive interactions. Nearly all intraspecific aggressive action patterns

were involved with maintaining spatial relationships between avocets.

In the winter avocets were gregarious and showed almost no aggres-

sive tendencies. In late winter and early spring aggressive activities

began to increase (Hamilton, 1969). At the time of arrival on the

breeding grounds there was still an oscillation between aggressive-

ness and non-aggressiveness. Ultimately avocets spaced themselves

into territories prior to nesting.

Intraspecific Aggression: Avocets had two threat postures

which were elicited when another avocet approached either on foot or

in the air. One was a crouch (Figure 14A) in which the approached

bird slightly flexed its legs and drew its head back close to its body.

The orientation of this display was usually toward the approaching

bird. The second was a simple raising of the interscapular feathers

while feeding. It seemed to function as a warning to reduce the

incidence of overt attacks (Hamilton, 1969). It was seen most often

in early spring in flocks of feeding birds and it also occurred when

two avocets approached one another near territory boundaries while

feeding.

More overt aggressive encounters occurred regularly and had

53

a somewhat ritualized form. If avocets approached too close to a

pair before territories were established, or invaded a territory later

in the season, the trespassers were immediately driven away. This

was accomplished by either one or both members of the pair pursuing

and chasing away the intruder. In either case the basic action pattern

was similar. The pursuing bird or birds ran rapidly after the ad-

versary with the head retracted somewhat and the body inclined

forward at about a 15' angle. When a single avocet pursued I have

termed it a single crouch-run (Figure 14B); and for a pair, paired

crouch-run (Figure 14C). The latter was the most common form of

pursuit before incubation began. It was most often directed at other

avocets, but was also used toward other species, particularly other

shorebirds. A bird being pursued usually ran or flew from the

scene (retreat; Figure 14B). The retreating bird often ran away

using a side step to keep its body perpendicular to the pursuing bird.

If the retreating bird did not leave quickly it would be charged by a

sudden flying assailment in which the attacker struck with its feet

on the other bird's back. This was accomplished by swooping in

close and kicking out with the feet (pursuit attack; Figure 14D).

In cases where spatial dominance was not clearly held by any

pair, complicated aggressive encounters involving several birds

often occurred. If neither pair retreated they met in a bowing

(Figure 15C) position in which all birds faced one another with

Figure 14, A. CrouchBe Single crouch-run: The bird on the left isdriving the bird on the right out of its territory(Retreating).Co Paired crouch-run: The pair on the left isdriving the other bird away.D. Pursuit Attack: The flying bird above isattacking.

pq

U

55

their bodies tilted forward and their bills near the ground or water.

Mates stayed close together and parallel to one another at all times.

if one pair was dominant, the encounter would go no further, the

dominant pair driving away the others using the paired crouch-run.

Where neither pair retreated, a melee of attacks occurred. One or

both members of a pair would jump at the opponents, either striking

out with a wing or attempting to land on another bird's back (jump

attack; Figure 15A). Immediately after an attack, pair members

quickly moved back to their side-by-side position. A bird trying to

avoid a jump attack either fluttered away or ducked entirely under

the water. If attacks did not occur, several other postures resulted.

Occasionally a bird would squat (Figure 15C) in the water or in some

cases it would squat and place its head in a resting position (pseudo-

sleeping, Figure 15C). One explantaion of these postures is that

they act to reduce aggression or act as appeasement displays. Ap-

peasement displays generally act to reduce fighting or inhibit attacks

and frequently expose some vulnerable area of the body (Manning,

1967). Observations of fighting avocets, however, do not support

the conclusion that these are appeasement displays, since birds in

either posture were often attacked or themselves attacked directly

from this position. A certain amount of pecking in the water, which

may be displacement feeding, also occurred under these stalemate

conditions.

Figure 15. A. Jump Attack: The bird with its wings up isabout to jump at the other bird.B. Wingspread.C. Grouping Display: The two pairs locatedthe right and left are in the bowing posture.Notice the closeness of the members of thepairs. The near avocet to the left is squattingand the near one to the right is pseudosleeping.

-13

56

57

These group encounters often included more than four birds

and I have observed as many as 12. A large number of birds taking

part suggests that some other function was involved besides spacing.

Birds seldom seek aggressive encounters on their own. There is

usually some advantage in doing so, such as territory establishment

(Mar ler and Hamilton, 1966). When an encounter began, avocets

would fly to the scene to take part, sometimes coming from several

hundred meters away. I feel that these fights have some sexual func-

tion and may act to strengthen the pair bond, but I have no confirma-

tory evidence. Often pairs just involved in aggressive interactions

began courtship activities, indicating that the stimulation generated

in fighting might be carried over as sexual arousal.

Territorial conflicts were usually characterized by single or

paired crouch-runs or a group encounter. However, when two birds

met along a territorial boundary which was not well-defined by land-

marks (such as those in open water), a parallel walk (Figure 18B)

would occur. Both birds walked from 0.5-1.0 m apart along the

territory boundary using a rather stiff deliberate stride with their

necks extended upward. Both frequently pecked at the water. This

usually continued for 20-60 sec and resulted either in both birds

turning and retreating into their own territories or in a series of

jumping attacks followed by retreat.

When avocets reacted to other species they used crouch, single

58

and paired crouch-run or pursuit attack. Most of the season they

were tolerant of non-predatory species such as other shorebirds and

ducks. However, during the early part of the parental care stage

no species were tolerated near the chicks.

Two other aggressive activities were associated with protection

of the nest and egg from predators. One was the predator chase in

which one to many avocets pursued and harassed potential avian

predators such as owls, hawks, and gulls. It included a pursuit

flight and a series of swooping dives at the predator. The harass -

anent persisted until the predator was far from the nest. A loud

alarm call was associated with this activity. If the bird was incu-

bating it returned immediately to the nest. The birds most com-

monly attacked were gulls (Larus californicus and L. delawarensis),

marsh hawks (Cirus and short-eared owls (Asio flamrneus).

The second aggressive action pattern used was the dive,

was directed at terrestrial predators which were in close proximi+7

to the nest. I have actually seen this used only toward humans, but

I suspect that it may also be used against other potential nest preda-

tors. An attacking avocet would swoop at high speed coming very

close to the intruder. I have actually been hit by wing tips as I

banded young in a nest. The flight between dives was characterized

by loud calls.

An inter specific threat display was also sometimes given. An

59

avocet, when suddenly encountering another species, would spread

its wings horizontally, crouch, and extend its neck forward (wing.-

spread; Figure 15B). This display was directed at an opponent and

was often accompanied by short charges. I saw this display directed

toward Killdeer (Chardrius vociferus) and ducks and geese. The

form of the display perhaps functioned to make the avocet appear

larger to an opponent.

Diversionary Behavior

Avocets exhibited several behavior patterns which functioned to

distract potential predators away from the nest or young. These ac-

tivities are those displays most often seen by humans visiting avocet

nesting grounds and have sometimes been misinterpreted in the liter-

ature

The most spectacular of the diversionary action patterns is fhe

tightrope display (Figure 16A). It is probably homologous to the

"broken wing" display of other shorebirds. The avocet held its

wings horizontal to the ground with its neck extended forward. The

tail was fanned and depressed. The bird walked along teetering from

side to side as if it were walking on a tightrope. The aspect of the

wing varied from a horizontal to vertical position. Often the display

was accompanied by a low croaking call.

The sneak-run (Figure 16B) display resembled the aggressive

60crouch-run action pattern, but the context was different. The avocet

ran with its head pulled back next to its body. It usually ran away

from the intruder. The function of this activity is unclear. It may

be similar to the "rodent run" display of some other shorebirds(Williamson, 1 950). To a human it seems to lack much value as a

means of distraction, but, of course, humans do not react in the

same manner as other animals. The crouch-run, tightrope and

breast dipping (Figure 16C) may alternate with one another in a

series of distraction displays. When breast dipping, an avocet ran

or walked in the water, stopping occasionally to bend at the ankle,

thus dipping its breast in the water. Hamilton (1969) feels that the

breast dipping display simulates incubation. This may be the origin

of the display but the fact that I have never seen it performed on land

and that the avocet spends only a second or two in the squatting posi-

tion seems to make fake incubation a doubtful function. Another

possibility is that it simulated an injured bird which was unable to

fly, but repeatedly tried to jump into the air.

When humans and probably other potential predators approached

or disturbed a group of nesting avocets, they were met with alarm

circling. Alarm circling consisted of one to many avocets flying in

circles and giving a loud alarm call. The circles were fairly large

and from 6 to 12 m above the ground. A bird may alarm circle, then

land, perform a tightrope, crouch-run, or breast dipping display,

Figure 16, A. Tightrope,

B. Sneak-run: The bird runs or rapidly walks inthis position when disturbed.

C. Breast dipping.

D. Flying,

A B

-,,,----

C D

61

62

and circle again. Sometimes a disturbed bird just stood and gave

an alarm call (Alarm calling).

All of the above diversionary activities may be combined in

sequences. Further, up to 50 birds may congregate and perform

distraction displays together. These groups of displaying birds

were usually located away from groups of nests. This activity usu-

ally persisted until the intruder approached close to the nests. Then

the group of displaying birds tended to break up and the pairs whose

nests were most closely approached kept displaying. If the nest was

found, they resorted to diving at the predator.

Nesting Behavior

Under nesting behavior I have included all activities associated

with selecting a nest site, nest building, egg laying, and incubation.

Avocets beg--In searching for a nest site even before they seleet-

ed a territory. Indeed, choice of a nest site may be an important

factor in determining the location of a territory. Although the nest

and the foraging territory (see Breeding Biology) may not be in close

proximity, the placement of the feeding area may be dependent on

having a suitable nesting area nearby. When seeking a nest site,

mates acted together by slowly walking over possible terrain with

their bills placed close to the ground (ground checking; Figure 17B).

They often stopped for varying lengths of time still performing this

63

activity. A characteristic vocalization usually accompanied this ac-

tivity and it seemed that the intensity of the calling was related to

the suitability of the site they were investigating. Ground checking

could change almost imperceptibly into throwing straws (Figure 17A)

in which the birds picked up pieces of grass and other materials in

their bills and tossed them toward the presumed nest site with a

sideways flip of the head. Hamilton (1969) states that the material

is tossed over the bird's back. This can occur on occasion, but it

is more common for items to be tossed sideways.

Throwing straws often led to scraping (Figure 1 7B) by which

the nest scrapes were hollowed out. The avocet rested on its breast

and hollowed out the nest scrape with its feet. Its wings were held

loosely at its side. Hamilton (1969) and Brown (1949) state that the

scrape is made with t the breast. My observations disagree, since

there were obvious scratch marks in newly formed scrapes. Also

scrapes were often found in substrate too hard to have been hollowed

out with the breast alone. Further, the avocets I watched seldom

rocked or rotated on their breast as Hamilton and Brown indicate.

Sometimes many scrapes were made before a final nest site was

chosen. The birds tended to return to favored spots many times

before the eggs were laid; however the final nest site was sometimes

different from any of the "favored" spots. I suspect that the nest

can be built in just a few minutes and the spot and time that the final

64

nest is built may be largely determined by the necessity for the

female to lay. Materials were added to the nest by throwing straws.

A great deal of material could be added to the nest in a short time in

this manner, since a nest could be built up several centimeters over-

night during a flood. Normally nests were built up slightly during

incubation.

Egg laying was observed in only one case. The female was

sitting on the nest. She suddenly stood up and began giving an excited

call similar to that used during ground checking. The male rushed

over and both called for several minutes. When I checked the nest

one egg was present; there had been no egg in the nest 30 minutes

earlier.

Once the eggs were laid and incubation had begun, both sexes

tended the eggs. An incubating (Figure 17D) bird sat on the nes with

its head held upright or in a resting position. During hot weather the

bill was held wide open and gular panting was evident.

An avocet relieving its mate at the nest went through a nest

approach (Figure 17C) ceremony in which it walked in a slow jerky

fashion while occasionally extending a leg posteriorly and shaking it,

As the bird approached the nest it often began to throw straws. At

this point, the incubating bird usually left the nest and began to throw

straws also. The relieving bird then moved to the nest and straddled

it and placed its bill among the eggs. The avocet erected its breast

Figure 17, A. Throwing Straws: The birds are picking uppieces of grass and tossing them with a flip oftheir heads.B. Scraping: The bird sitting on the ground isscraping. The other is ground checking.C. Nest approachD. Incubation

A

65

\B

if

66

feathers and settled on the nest. It then used its legs and feet to

rotate the eggs. Head bobbing sometimes also occurred during the

nest relief ceremony.

Parental Behavior

Avocets were very aggressive while caring for their young.

They excluded all species from the territory around the chicks.

Many aggressive action patterns suchas single crouch-run, pursuit

attack, crouch, parallel walk and wingspread were used.

The young were brooded (Figure 18C) during the first two weeks.

The parent rested on its tarsi and the chicks stood against the breast.

The adult's wings were usually drooped slightly to provide extra pro-

tection for the young. At least one parent was always in attendance

of the chicks. It usually stood neaz by, usually in the taaright (Figure

18A) posture, which is an alert posture. The parents relieved each

other at intervals just as incubating birds did, but there seemed to

be no ceremony involved.

When the nest was located away from a feeding area or the

chicks were in an area prone to disturbances, the parents moved

the chicks. This was done by leading, where both parents walked

ahead of the chicks while continually calling to them. If the adults

were particularly excited they would run or fly ahead, calling, and

then come back to the chicks in an attempt to get them moving.

Figure 18, A. Upright: This bird is standing with its head

extended upward.

B. Parallel walk These two males are walking

side by side in a territorial boundary conflict,

C.

Skt.

A

B

67

68

The parents also had alarm calls which warned the chicks of

danger. The chicks ran for cover and laid flat on the ground upon

hearing the parent's call.

Miscellaneous Action Patterns

In any functional categorization of behavior some action patterns

are difficult to classify or do not fit neatly into any functional group-

ing. The upright posture is one of these. It occurred at all times

of the season and at almost any time A bird in the upright posture

stood or walked with its head and neck extended vertically. This

action pattern seemed to be used when a bird was disturbed or on

the alert.

Another display which does not fit well into any category is

head bobbing, in which the head is pumped up and down rapidly. It

sometimes was used in nest exchange ceremonies, some aggressive

encounters, or when the bird was disturbed in some way, as when a

human approached.

69

THE TIME BUDGET ANALYSIS

Time budgets express the manner in which animals partitiontheir time among various activities. Time budgets can be expressedin two basically different wars. One is a frequency-based time bud-get, the other time-based. The frequency type may give a record ofwhat a bird has done during a one minute or five minute time interval,for example. The result is a sample of the bird's activities throughtime. The frequency with which an animal performs various activitiesduring the time interval may also be recorded. For example, thenumbers of preening movements in an hour or day could be tabulated.In either case, the activity is measured as a frequency pei time inter-val, but the actual amount of time devoted to various activities cannotbe determined.

In the second method, the actual amount of time spent in eachactivity is recorded. It can be expressed as a total time observedfor the activity; for example, if 20 hr, were spent collecting data,the amount of time spent preening might be 30 min.out of the 20 hr.(see Verbeek, 1964). Another approach is to express the time spentin each activity as a percentage of the total observation time. Thelatter method offers the most meaningful representation and it isnot greatly influenced by the length of the activity period of the birds.It also has sufficient abstraction to allow comparisons between stages

70

of the breeding cycle.

I have utilized a combination of the frequency and time ap-

proaches. By selecting a small unit of time (10 sec.) in which to

sample behavior I have essentially measured the total time spent in

each activity. This has allowed me to express the avocet's time

budget as a percentage of the total time available to the bird.

I will consider both seasonal and diurnal time budgets, drawing

inter-sexual comparisons in each case. Proper seasonal and diurnal

apportionment of time requires different strategies and each is acted

upon by slightly different selective pressures, thus demanding that

each be considered separately. Further, many species exhibit very

different male and female roles in their social systems, and thus

examination of sexual differences in the seasonal and diurnal time

budgets is also important.

Time apportionment data for 40 action patterns (Table 5) of

both sexes for both seasonal and diurnal patterns are presented in

Appendices 1 and 2. In order to analyze the time budgets more

meaningfully I have grouped action patterns according to their gen-

eral functions (Table 6).

Behavioral Categories

Several of the categories presented in Table 6 require further

explanation. The maintenance activities have been divided into four

71

Table 6. Categories of behavior used in the time budget analysis

Category Included Action Patterns

Feeding feeding

Resting resting

Preening preening

Other Maintenance bathing wing-leg stretchscratching wingshaketwo-wing stretch drinking

Aggressive Behavior crouch bowingsingle crouch-run squattingpaired crouch-run pseudosleepingpursuit attack parallel walkjump attack wing spreadretreat

Diversionary Behavior

Mating Behavior

predator chase breast dippingtightrope alarm circlingcrouch-run alarm calling

neck extendedprecopulatory preeningmountcrossed billspostcopulatory walk

Nest Building Behavior ground check ingscrapingthrowing straws

Incubation incubation

Upright upright

Parental Care broodingleading

Absent out of view

72

categories. This was done because of the relatively large amount

of time spent in feeding, resting and preening. The aggressive cate-

gory consists of those action patterns most consistently used in intra-

specific encounters. Most interspecific behaviors are used in attack-

ing and fending off predators; therefore they are included in the

diversionary category. The nest building classification consists

of those activities associated with selection of a nest site and build-

ing a nest. Incubation is included as a separate category. The

absent category represents the time when an avocet was lost from

view for more than a few seconds during an observation period.

This category was necessary to maintain continuity during observa-

tions.

The Seasonal Time Budget

The seasonal time budget consists of a representation of the

time spent in each category of behavior for each stage of the breed-

ing cycle. I have combined the data for both sexes for this section

of the analysis. The time budget is graphically represented in

Figure 19 and a tabular presentation of the same data is included

in Appendix 3. The apportionment of time into each category of

behavior will be discussed below with emphasis on the possible eco-

logical and behavioral bases for the patterns found.

Feeding (Figure 19A): From an ecological point of view, the

Figure 19. (A-K). The seasonal time budget (data for bothsexes combined) expressed as the percent oftotal observation time spent in each category ofbehavior. The stages and sample sizes are:Stage 1 Prenesting 4298.0 min.Stage 2 Incubation 18159. 4

Stage 3 Parental Care 2362. 7

Stage 4 Po stbr eeding 276 7. 1

50A FEEDING

40 -

30

0<h-

- 20-I-

I 0 -

w>

030.J

C PREENING D OTHER MAINTENANCEO

40 -

B RESTING

I-

w -5

w 30 -

20 -

10 -

73

E AGGRESSION

-5

I 2 3 4 2 3 4

STAGE

DIVERSIONARY NEST BUILDING

74

G MATING J PARENTAL CARE

UPRIGHT

4

4

STAGE

2 3 4

75

amount of time spent feeding is probably the most interesting and

possibly one of the most important aspects of a bird's time budget.

The expenditure of time in foraging in the four stages of the breeding

cycle is significantly different. There are several possible explana-

tions for these differences, each relating to avocet energy require-

ments. This aspect of the time budget will be considered more fully

in the Discussion.

Resting (Figure 19B): The percentages of time spent resting

through the breeding cycle had a pattern similar to that found for

feeding. The low proportion of resting time in Stage 2 is probably

deceptive. The birds were spending about 43 percent of their time

incubating during this stage. In some large species, such as the

Willow Ptarmigan (Lagopus lagopus) and Ring Dove (Streptopelia

risoria), incubation does not increase metabolism over the resting

level (West, 1968; Brisbin, 1969). Combining rest and incubation

activity for Stage 2 gives a total of 47 percent of the time spent in

an "inactive" state. In Stage 3 only 90 5 percent of the time was

spent in resting. There was, however, a large amount of time

spent in the upright posture, which involves merely standing with

the head and neck extended upward. If upright is considered to be

relatively close to resting in its energy requirement, then the actual

"inactive" time in Stage 3 is close to 41 percent. If this line of

reasoning is correct, avocets at Summer Lake appear to spend a

76

rather constant amount of time through the breeding cycle in an

"inactive" state.

Preening (Figure 19C): The percentage of time spent in preen-

ing remained essentially constant through the first three stages of

the breeding cycle, increasing in Stage 4. Care of the body surface

probably required the same amount of time throughout the breeding

season, but with the onset of post-nuptial molt (Stage 4) there was

an almost two-fold increase in preening time.

Other Maintenance Activities (Figure 19D): Very little time

was spent in the remaining maintenance activities, and there was no

seasonal fluctuation in these activities. Body maintenance should be

constant throughout the breeding season since the body needs continual

care regardless of the time of year.

Aggressive Behavior (Figure 19E): Aggressive activities took

very little of the avocet's time (a maximum of only 2. 4 percent in

Stage 3). Despite this, a casual observer of avocet behavior undoubt-

edly would conclude that they spend a great deal of time in aggressive

activities. This impression stems from the pattern of distribution

of aggressive activities in time. During Stage 3, 18 min/day were

spent in aggressive activities. Each encounter lasted approximately

10 sec; thus an avocet was involved in about 92 aggressive encounters

per day, or about one every 7.5 minutes. Thus while the frequency

of aggressive actions is relatively high, the time expenditure is not.

77

A time budget gives the more realistic view of how much time was

actually spent in aggression. However, behaviorally, the frequency

at which an action pattern occurs may be functionally more important

than the time actually spent on the activity. For example, it may be

more adaptive for avocets to spread 18 min. of aggressive activity

throughout the day rather than concentrate it in one short time span.

On the other hand, energetically, avocets may not be able to efficiently

spend more than 18 min, on aggression.

The greatest amount of time spent in aggression was during

Stages 1 and 3. This was associated with territorial establishment

in Stage 1 and parental care in Stage 3. Aggressive activity was low

in Stage 2, possibly because the territorial system was stable and

approximately half the birds in the population were incubating and

thus not free to engage in aggressive encounters.

Diversional_2yBk-havior (Figure 19F): An extremely small

amount of time was spent in diversionary activities and that only in

Stages 2 and 3. These stages include incubation and parental care.

Protection of eggs and young may contribute to the appearance of

diversionary activities during these times. The small amount of

time spent in these activities may be due in part to the rigorous

control of predators on the management area.

Mating Behavior (Figure 19G): Mating activities took about 2

percent of the avocet's time in Stage 1. A typical courtship sequence

78

took about 2 min. to complete. Thus, on the average, a pair copulated

or attempted copulation about seven times a day through the month

duration of Stage 1,

Nest Building Behavior (Figure 19H): A fairly large portion

of time was allotted to nest site selection and nest building during

Stage 1. From field observations I suspect that avocets can build

an adequate nest for the laying of the first egg in a few minutes.

They spent most of their nest building time,however, making numer-

ous scrapes and adding lining to some before the first egg was laid.

I doubt that the sole function of this nesting behavior is to build a

nest; strengthening the pair bond may be an important function as

well. The nest building activity which occurred in Stage 2 was asso-

ciated with maintaining the nest structure.

Incubation and Par ntal Care (Figure 19 I -J) I have combined

these two categories here because both are used to care for objects

of the reproductive effort. Incubation took 43.5 percent of the time

in Stage 2 while parental care required 8.4 percent in Stage 3. How-

ever, this does not accurately represent the time spent caring for

the young. The Upright position was used a great deal while watch-

ing over the chicks. This took 31. 7 percent of the time in Stage 3.

If upright is included as part of parental care, this increases paren-

tal care to 40.1 percent of the total time, which is similar to that

spent in incubation. Therefore, care of the eggs and chicks took

79

about the same amount of time.

Upright (Figure 19K): I feel that the upright posture is essen-

tially an alert position assumed when an avocet is watching something

or is wary. It is an indication of the general alertness of the birds

during different stages of the breeding cycle. The birds were most

alert when caring for the young. In Stages 1, 2, and 4 the time spent

in this activity went from 4.5 percent to 1.0 percent. This pattern

is as one might expect. In Stage 1, when the territory was being

established, the birds were comparatively more alert; in Stage 2

the territory was less rigorously defended, while in Stage 4 there

were no territorial activities. Also, a certain undetermined amount

of time spent in the upright posture was due to my being close to the

birds.

Absent (Appendix 3): I only recorded the absent category in

Stages 2 and 3. It represents the time the avocets under observation

were not in my view during an observation period. This accounts for

9 percent of the time in Stage 2. Part of this was due to the bird's

feeding on a territory located some distance from the observation

tower, thus making them difficult to observe.

Sexual Differences in the Seasonal Time Budget

The percentages of time that males and females spent perform-

ing the basic categories of behavior (Table 6) are presented in

80

Figure 20. An asterisk has been placed above each male-female

comparison which shows a significant difference (P <.05). These

data are tabulated in Appendix 4.

A survey of Figure 20 indicates that there are only seven male-

female comparisons which show statistically significant differences.

There are two possible reasons for the small number of differences:

the data may be insufficient to determine if the differences observed

are real, or there may actually be no differences between the sexes.

I suspect both are right, in part. Five of the seven significant differ-

ences observed occurred in Stage 2, where the most data are avail-

able. There is a possibility that with more data for the other stages

there would be more significantly different comparisons. In contrast,

considering the generally similar behavior patterns of the sexes, the

lack of time budget differences is not surprising.

I will not rely heavily on statistical evidence for real differences

because statistical methods do not always reveal biological signifi-

cance. For example, there may be sexual differences in the time

budget which can be shown to be adaptive but are not statistically

significant, or the opposite situation might occur. Therefore, I will

attempt to explain differences between the sexes when there are

plausible explanations.

Feeding (Figure 20A): The male consistently spent more time

Figure 20. (A.K). The seasonal time budget for both sexes,expressed as the percent of the total observationtime spent in each category of behavior by eachsex. Stages are as in Figure 19, Sample sizes(min. ):

Stage 1 23 21 . 0 2076. 7Stage Z 10565, 7 7594. 2Stage 3 1189.7 1173.0Stage 4 13930 5 1373.6

FEEDING

40

30

20\

B RESTING

male

El female

10

40

30

20

10

PREENING

111 011INNIU\

OTHER MAINTENANCE

4

STAGE

81

10 -

W

- I -1--

z0F:< 5>CrLUcr)co0I<II 40-Izw0cew 30a_

F DIVERSIONARY

rwrrTini---41. li----MllG MATING

20 -

I0

INCUBATIONI

H NEST BUILDING

82

PARENTAL CARE

1 2

K UPRIGHT

03 4 1

STAGE2 4

83foraging than the female in all stages except Stage 1. The female

may have needed to feed more in Stage 1 because she was producing

eggs, which is an energetically expensive process (El-Wailly, 1966;West, 1968). The reason why the male fed more than the female in

the other stages is unclear.

Resting (Figure 20B): The sexual differences for time spent

in resting are small in every stage of the breeding cycle. The Stage

2 comparison demonstrates a statistical difference. The female may

have rested more in the early phases of Stage 2 because she was

recovering from egg production.

Preening, Other Maintenance Activities, and Aggression (Fig-

ure 20 C-E): There was little difference between the sexes for these

activities.

Nest Building Behavior (Figure 20H): The male spent slightly

more time ground checking, throwing straws, and scraping than thefemale. The sequence of action patterns involved in nest building

may account for this difference. A pair searching for a nest site

usually ground checked together, but when scraping began the male

tended to scrape while the female stood close by in an upright pos-

ture. This seems to be adaptive since the scraping position is

awkward making quick reaction to avian predators difficult.

Incubation (Figure 201): The sexes shared incubation duties,

but not equally. The female spent about 6.5 percent more of her

84

time on the nest than did the male. The difference, however, was

not distributed evenly through the incubation period (Table 7). The

male incubated more during the first third and the female more dur-

ing the latter two-thirds.

The Diurnal Time Budget

The diurnal time budget was partitioned into six 2-hr periods

from 0600-1800. The percent time spent in each category of behavior

for each period is given in Appendices 5 and 6. The seasonal changes

in the diurnal time budget (sexes combined) are presented in Figure

21,

Feeding (Figure 21A): The diurnal distribution of feeding ac-

tivity was bimodal in all stages but Stage 3. Avocet feeding peaks

occurred in the morning and afternoon. The magnitude of the, morn-

ing peak is not really known because I do not know whether the amount.

of time spent feeding was rising to a high point in Period 1 or whether

it was decreasing to that point. The increase in feeding in the after-

noon was dramatic in Stages 1 and 4 and much more muted in Stage 2.

The morning trough in the feeding corresponds closely to the peak

of resting (Figure 21B). The muted peaks seen in Stages 2 and 3 are

probably related to the effects of incubation and parental care. A

constant amount of time was spent incubating throughout the day

(Figure 21 1). This forced the birds to modify their feeding pattern

Table 7. Diurnal incubation pattern for each sex

Time of Day percent observation time N(min. )

percent observation time(min. )

0600-0800 3L2 1740 50.3 1439

0800-1000 40.9 1320 46.0 1320

1000-1200 43. 8 1620 43.4 1620

1200-1400 37.2 1050 49.2 1050

1400-1600 47.9 1289 38.4 1289

1600-1800 34.1 900 48. 1 900

MEAN 39.6 7919 45.7 7618

Figure 21, (A-K). The diurnal tim e budget for the four breeding cycle stages expressedas the percentage of the total observation time spent in each category ofbehavior for each of six diurnal time periods (both sexes combined). Stagesare as in Figure 19.

0600-0800

Sample sizes (min):0800- 1000-1000 1200

1200-1400

1400-1600

1600-1800

Stage 1 614. 6 1137.1 776.8 539.5 716. 7 693.2

Stage 2 3060.9 2572.6 3215.8 2088.5 2554.9 2188.0

Stage 3 468.2 60.0 414.3 297.3 118.4 982.6Stage 4 177.6 496.2 472.5 423.2 599.8 478. 3

80

60.

40-

I017-: 20

m011OI 801zcrIL

20

A FEEDING

stage I stage 2 stage 3 stage 4

\-[

86

B RESTING

stage I stage 2 stage 3 stage 4

I 2 3 4 5 6 I 2 3 4 5 6 I 2 3 4 5 6 2 3 4 5 6TIME PERIOD

C PREENING

stags I stags 2 stage 3 stage 4

87

OTHER MAINTENANCE

AGGRESSION

DIVERSIONARY

TIME PERIOD

40

20

W2 15p:

z0i=aaxWcocoO-JI-0I 801zWC.)crW 60a.

40

20

G MATING

stage I

+-..... ..."'

I INCUBATION4.--+++-4t

stage 2

. ,NEST BUILDING

K

/+\+---4

stage 3 stage 4

88

// \.\t

UPRIGHT

,4-..... + --- 4. _ + 1.

OAR'ENYAL CA'REI

I 1

1 2 3 4 5 6,

1 2 3 4 5 6 I 2 3 4 5 6. "I

+I 2 3 4 5 6

TIME PERIOD

89

around incubation.

Resting (Figure 21B): Nearly all the resting done by avocets

occurred during a 2-4 hr period in the morning. This peak was not

as evident in Stages 2 and 3. Resting increased somewhat in the

afternoon in Stages 1, 3, and 4. An explanation of the adaptive na-

ture of this resting pattern will be offered in the Discussion section.

Preening (Figure 21C): The percentage of time spent preening

also showed a bimodal distribution around the morning rest period.

The amount of time spent in activities such as preening is probably

dictated by higher priority behavior patterns such as feeding, resting,

and incubation.

Other Maintenance Activities (Figure 21D): The most obvious

feature of this category is the lack of diurnal pattern. The reason

for this is simple. Activities making up this category are such

things as scratching, stretching, drinking, and bathing. These

occur in response to stimuli which may occur at any time.

Aggression (Figure 21E): One would expect aggressive encoun-

ters to be most frequent when avocets are the most active. The data

indicate this to be the case.

Diversionary Behavior (Figure 21F): Avocets only defended

against potential predators during Stages 2 and 3. The diurnal pat-

tern of diversionary activities was probably closely related to the

activity patterns of other species, since avocets reacted to potential

90

predators only when they came near the nest or young.

Mating Behavior and Nest Building (Figure 21G-H): Mating

activities took place predominantly in the morning but were never

observed during the morning rest period. A basically similar pattern

was apparent for nest building. Perhaps during Periods 1 and 3 ac-

tivities such as feeding were not taking a large amount of time during

the morning leaving time for mating and nest building (see Discussion).

The nest building in Stage 2 was concerned with maintaining the nest

and was usually done during nest exchanges. This accounts for the

lack of diurnal variation.

Incubation and parental care (Figure 21 I, 3): As would be ex-

pected, there were no diurnal changes in incubation, since the eggs

were covered almost continually. There was a slight tendency for

the proportion of time spent in parental care to decrease as the day

wore on.

Upright (Figure 21K): There was very little diurnal fluctuation

for the upright posture during Stages 1, 2, and 4. The posture is

used in this stage to watch over the young; the young, like the adults,

tend to feed more in the afternoon. The increased watchfulness may

reflect the need for a closer watch on the chicks as they feed. This

peak may also be a reaction to the increased activity of other species

in the afternoon.

91

Sexual Differences in the Diurnal Time Bud et

A survey of the sexual differences in the diurnal time budget

reveals that the sexes have similar budgets (Figure 22). These data

are tabulated in Appendix 6. Of 180 possible comparisons only nine

were significantly different (P <.05). Considering that the sexes

had very similar seasonal time budgets, this result is not surprising.

The small sample sizes for many time periods and the scat-

tered nature of the statistically significant differences make interpre-

tations difficult. The sexual differences in the diurnal pattern of

incubation are interesting, however. The female incubated more than

the male in the morning and they tended to alternate incubation

duties during the afternoon (Figure 221), There are two possible

explanations for the afternoon alternation. It could represent a

response to heat stress, since incubating avocets were exposed to

high temperatures (> 370 C) in the afternoons. Frequent breaks

from incubation duties could have helped reduce the heat stress.

Another possible explanation is associated with optimal feeding

times. There may be advantages to feeding predominantly in the

afternoon (see Discussion). By alternating incubation duties often

in the afternoon both sexes could exploit this situation. The feeding

pattern in Stage 2 had a similar but opposite pattern of alternation,

suggesting that feeding and incubation patterns are interrelated.

Figure 22. (A-K) The diurnal time budget for the four breeding cycle stages, expressed as the

percentage of the total observation time each sex sp ent in each category of behavior

for each of six diurnal time periods. Stages are as in Figure 19 and time periods as

in Figure 21. Sample sizes (min):

Stage1 2 3

Period4 5 6

300.1 320.2 519.9 569, 4 389.8 389. 7 299.4 269, 2 359.1 363, 1 359.6 365. 6

2 1639.4 1438.6 1469. 1 1319.0 1622.8 1619.6 11049.3 040.1 1288.6 1286.6 1299.2 899. 5

3 239.5 239.7 29.9 29.8 209.4 208. 5 149.9 1 49. 8 58.0 59.0 496, 6 499. 1

4 90, 6 90, 0 299.3 300.5 2 42.3 240.7 213.0 209.5 299.9 299.9 239.7 239.4

90

70

50

30

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90

70

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stage I stage 2 stage 3 stage 4

B RESTING

male

ri female

3 4IN'

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PERIOD4 5 6

15

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V%2=40; AMAAim

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3 4 5 6 1 2 3 4 5 6 I 2

PERIOD

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4 5 6 3 4 5 6

40-

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UPRIGHT

stage I stage 2 stage stage 4

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PERIOD

95

DISCUSSION

Avocet evolution has resulted in a system of integrated tactics

by which they exploit their environment. These span a broad range,

including the type of mating system, pattern of spatial dispersion,

nesting requirements, breeding season, clutch size, parental care

system, age and size distribution, age at first breeding, longevity,

timing of molts, and migration (Pitelka, pers. comm.). The activi-

ties involved in this tactical design all require energy. Some require

more than others; therefore, the birds must organize their activities

so that they have sufficient time to feed and gain needed energy. The

relationship, then, between energy demands and the allotment of

time to various activities is probably one of the most important ele-

ments in the evolution of a successful exploitation system.

I have measured the time element, or the allocation of time to

activities, and I now will discuss the adaptive nature of the avocet's

seasonal and diurnal foraging pattern in relation to energy require-

ments. I will also briefly delve into the apportionment of time to

non-foraging behavior, and how this relates to the energy budget.

Finally I will attempt to relate the roles of the sexes in the social

system.

96

Energy and Seasonal Changes in Foraging Activity

Since an individual obtains the necessary energy to carry on

life processes by feeding, its energy demands should rather directly

affect the amount of time spent feeding, as modified by food density

and availability. The energy required by any individual is dependent

on several factors; these include weight, ambient temperature, ac-

tivity levels, and such energetically expensive processes as egg

production, molt, and prernigratory fat deposition. Therefore, the

adaptiveness of the allocation of time to foraging during the breeding

season can perhaps be explained by the relationship between the

avocet's energy needs and the availability of food and time (Figure

24).

There is an approximately inverse linear relationship between

temperature and standard metabolic rate for a bird of a certain we,et

(Kendeigh, 1970; King and Farner, 1961). Resting avocets (mean wt,

g) at 30°C require about 33 Kcal/bird/day while at 0°C the

standard metabolic rate is about 92 Kcal/bird/day (see Appendix 7)0

The daily mean ambient temperature at Summer Lake generally

increased throughout the breeding season (Figure 23). One would

therefore expect a corresponding decrease in the standard metabolic

rate from early to late in the breeding season. Other factors aside,

the decrease should be reflected in a decrease in the foraging time

Figure 23. The seasonal temperature regime for SummerLake, Oregon during 19 69. The daily maximumand minimum temperatures were obtained froma U. S. Weather Bureau station located approx-imately 2 mi from the study area. Temperaturesare averaged for 15 day periods.

30

25

20

15

I0

daily maximum

daily minimum

APRIL MAY JUNE JULY AUGUST

Figure 24, Generalized relationships between time spent infeeding by avocets and energy demands. The sizeof the boxes under feeding time represents theamount of time spent foraging in each stage of thebreeding cycle. The width of the arrows indicatesthe relative effect each factor has on the amount oftime spent feeding in each stage. The dashed lineindicates a contributing effect.

ENERGY NEEDS

98

TIMEFEEDING ENERGY AVAILABILITY

/

PREY

ABUNDANCE

ACTIVITY

99

(Figure 24). Such a relationship has been established for wintering

Brewer's Blackbirds (Euphagus cyanocephalus) under field conditions

(Verbeek, 1964).

Activity or physical exertion is energetically expensive and

adds to energy requirements. Kendeigh (19 70) feels that most of the

increase in energy requirements over standard metabolism is due

to the amount of locomotor activity taking place. For example, fly-

ing increases metabolic rate 5 to 20 times (Tucker, 1969). Avocet

energy requirements should, therefore, be higher in stages of the

breeding cycle with the highest levels of activity (Figure 24, Table 8).

Avocets must go through several energetically expensive proc-

esses during the breeding season. These are egg production, the

postnuptial molt, and premigratory fat deposition. Egg production

has been shown to significantly increase energy needs in the Willow

Ptarmigan (wt. 571 g), which expends about 22 Kcal/female/day in

egg production. This represents a 21 percent increase over standa,rd

energy demands for that time of year (West, 1968). Egg production

has also been shown to be energetically expensive in Zebra Finches

(Taeniopygia castanotis) causing a 13 percent increase in standard

metabolic rate (El-Wailly, 1966).

The post-nuptial molt also increases energy needs. West (1968)

found that Willow Ptarmigan used about the same amount of energy in

molting as in egg production. Domestic fowl increase energy needs

Table 8. Percent total observation time spent in an "active" state for each stage of the breeding cycle.*

Stage 1Activity level (%)

Stage 2 Stage 3 Stage 4

including feeding 48. 8 25.0 43. 4 48. 7

excluding feeding 12.4 1.9 12.5 . 7

*Activity levels were determined by adding the percent time spent feeding, other maintenance,aggression, diversionary, courtship, nest building, and parental care.

1 01

during molting by 45 percent (Perek and Sulman, 1945) and molting

Emberiza hortulana increase metabolism by 62 percent (Wallgren,

1954). Lustick (1970) found that Cowbirds (Molothrus ater) used 13

percent more oxygen while molting. In addition, 13 percent more

oxygen was used for increased thermoregulation due to decreased

feather insulation at 35 C.

During premigratory fat deposition there is a shift in energy

storage from glycogen to fat. This shift is also accompanied by

hyperphagia (King and Farner, 1961). Morton (196 7) found that

White-crowned Sparrows (Zonotrichia leucophrys) increased food

intake by 20 percent during vernal fattening. Egg production, molt,

and premigratory fattening increase energy requirements and they

should influence the amount of time spent feeding in the stages in

which they occur (Figure 24).

Energy needs cannot be directly related to the amount of time

spent foraging, however, because food abundance, availability, ard

quality may vary through the breeding season. Avocets feed pri-

marily on aquatic insects and aquatic vegetation (Wetmore, 1925).

The seasonal changes in the abundance and availability of these food

items should influence the amount of time the avocets must spend

foraging. The patterns of seasonal fluctuation in insect abundance

at Summer Lake are not known, but data are available for the

Whistler's Bend Impoundment, located 17 km northeast of Roseburg

102

in southwestern Oregon (Coche, 1964). The magnitudes of abundance

and the species present in the two areas are probably not the same,

but there should be a general correspondence in the pattern of sea-

sonal abundance. Aquatic insect populations in the impoundment be-

gan to increase in. March and reached high levels by July (Figure 25).

Coche's data indicate insect abundance as numbers of emerging

adults. Therefore the insect larvae available to avocets would be

at their largest size and greatest abundance from 1 to 2 weeks before

the emergence (N. Anderson, pers. com. ). This means that avocets

would probably need to spend more time in feeding early in the breed-

ing season and less later on to obtain the same amount of insect food.

Verner (1965) found that the Long-billed Marsh Wren (Telmatodytes

palustris) consumed 4.3 percent more energy in May than June but

spent 30 percent more time feeding in May. He felt this difference

was due to differences in insect abundance. A similar situation

has been found for Red-winged Blackbirds (Agelaius

(Hintz and Dyer, 1970). It is possible that avocets at Summer Lake

fed primarily on vegetation early in the season due to low abundance

of insect prey. This tactic would probably increase the total amount

of time required for feeding activity, however, since vegetation has

about 20 percent less caloric value per gm dry weight than insects

(Southwood, 1966). It should also be remembered that avocets can

probably not utilize the cellulose portion of plants.

Figure 25. Seasonal pattern of aquatic insect emergence forthe Whistler's Bend Impoundment, Douglas County,Oregon. Estimates of the number of emerginginsects were obtained from trapping. Chironornini,Tanytarsini, Orthocladiinae, Ablaesmyia, Proladius,Ephydridae, Ephemeroptera, and Coenagrionidaewere included. Modified from Coche (1964).

z 0

NU

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104

Body weight undoubtedly affects energy balance. When energy

requirements are high the birds must either feed enough. to keep up

with energy demands or they will lose weight. This factor may some-

what lower the amount of time spent in foraging during one stage and

feeding might later be increased to rectify the weight loss.

The foraging time budget for the four stages of the breeding

cycle (Figure 19A) appears to be affected by a combination of the

above energy needs. This is summarized in Figure 24. Stage 1 had

the second highest feeding level. Several factors appear to contribute

to this, such as the low environmental temperature and food abun-

dance, high activity levels, plus egg production. In Stage 2 time

spent feeding dropped to its lowest level. This may be accounted

for by the higher ambient temperature, greatly reduced activity

level, and greater prey abundance. The foraging level increased

in Stage 3 in spite of Ligher temperatures and the greatest prey

abundance. The high activity level associated with the care and

protection of the young perhaps accounts for the increased foraging

time. Stage 4 had the highest feeding level, yet temperature and

prey abundance should have been at a high at that time. In addition

activity levels were very low. The post-nuptial molt and premigra-

tory fat deposition were occurring during this stage and I believe

these two processes account for the large allocation of time to

feeding.

1 05

Energy and Seasonal Patterns in Non-feeding Activities

The pattern of the seasonal foraging time budget appears to be

largely controlled by energy requirements during the breeding cycle.

It must be remembered, however, that the amount of time spent

foraging is bacially dependent on the size of the bird, temperature,

and food availability. The allotment of time to all other activities

is determined by the ability of the birds to gain the extra energy

to perform them. A successful species must have evolved a social

system in which the allotment of time and energy to various activities

does not exceed the minimum time needed to obtain sufficient energy.

Therefore, one would expect selection to reduce the time spent in

energy-demanding activities to a minimum. For example, aggres-

sion should not take a large portion of time or energy. Further, one

would expect evolution of a nesting strategy which would offer the

least contact with predators and thus lessen time spent for diversion

and nest defense.

The allocation of time to physically demanding activities such

as aggression and diversionary activities was small for avocets at

Summer Lake (Figure 19). Similar situations have been found for

Marsh Wrens and Dickcissels (Verner, 1965; Schartz and Zimmerman,

19 71).

All animals apparently need rest. The physiological reasons

106

for rest are unclear, but it may have evolved in relation to energy

needs. By reducing metabolic rate to a minimum during a large

portion of the 24-hour cycle, energy can be conserved, especially

during the night when it is not feasible for diurnal animals to feed.

Further, one might expect an animal to rest most when energy de-

mands are the greatest. I found no evidence that avocets changed

the amount of time spent in an "inactive" state during the day in

relation to energy requirements.

The Bimodal Nature of the Activity Pattern

The avocet's diurnal activity pattern was characterized by two

peaks of activity separated by a period of inactivity occurring in mid

to late morning (Figure 26). This pattern was represented in many

categories of avocet's behavior (Figure 21). A similar bimodal

diurnal activity patte r, has also been found for a wide variety of

animal taxa, including insects, arthropods, mammals, and birds

(Aschoff, 1966). The details of these diurnal activity patterns are

different for different species but all are ultimately related to the

time phasing of environmental conditions (Palmgren, 1949; Aschoff,

1964; Verner, 1965). This implies that a diurnal pattern of activity

is adaptive and a product of natural selection.

Figure 27 summarizes the organization of the diurnal time

budget on a seasonal basis for several categories of behavior. The

Figure 26. The apportionment of avocet's time to an "active"state. The percent time active was obtained bysumming the percent total observation time offeeding, mating, nestbuilding, in parental care,aggression, other maintenance, and diversionaryactivities.

70

60

50

40

30

20

10

107

0600-0800 0800-1000 1000-1200 1200-1400 1400-1600

TIME OF DAY

1600-1800

Figure 27. The apportionment of time by avocets to 7 categoriesof behavior for six diurnal time periods over theentire breeding season. F = feeding; B = resting;P = preening; A = other maintenance, aggressiondiversionary, courtship, and nestbuilding; I = incu-bation; U = upright; PC = parental care; and Babsent plus other unaccounted for time

108

0600 0800 1000 1200 1400 1600to to to to to to

0800 1000 1200 1400 1600 1800

TIME OF DAY

1 09

only categories which varied appreciably through the day were feeding

and resting. It is also apparent that the diurnal pattern of feeding

corresponds closely with the overall diurnal activity pattern (Figure

26). Therefore foraging appears to be the major factor in determin-

ing its form. The feeding pattern, in turn, is related to features of

the environment (Figure 24). Therefore a closer look at the adap-

tiveness of the diurnal foraging pattern should offer insight into the

adaptiveness of the bimodal activity pattern.

Since feeding is synonymous with energy procurement, its di-

urnal distribution should reflect patterns of an individual's diurnal

energy requirements given constant food availability. The morning

feeding peak was evident in nearly every breeding cycle stage (Figure

21), I believe that this feeding peak occurred because the birds had

not fed for 6 to 10 hours and they had to feed in the early morning to

make up the energy debt incurred during the night. Red-winged

Blackbirds seem to show a similar response to the night-long fast

(Hintz and Dyer, 19 70). The height of the morning feeding peak

should be related to the energy demands placed on the birds during

the night. The highest morning feeding peaks occurred in Stages 1

and 4. Night temperatures were probably a major factor contributing

to the increased feeding time in Stage 1 (Figure 28) and the demands

of the post-nuptial molt and premigratory fat deposition were probably

important in Stage 4, During Stages 2 and 3 there were lower

Figure 28. The diurnal foraging pattern for avocets atSummer Lake. The diurnal temperatureregime from Cabin Lake, Oregon, located40 mi from Summer Lake. The diurnalpattern of emergence of Tricoptera atMontreal, Quebec (expressed as a percent-age of the occasions on which the highestcatch of the day fell at a certain time) (fromCorbet, 1966). The only relationship betweenthese curves are those made through infer-ence in the text by the author.

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111

night-time energy demands due to higher temperatures and a shorter

period of darkness; the morning feeding peaks were correspondingly

lower. These peaks may also be lower because the birds had more

time to feed in the morning prior to the observation periods. The

relative heights of the morning feeding peaks are not due entirely

to the energy demands of early morning. Food abundance is probably

also an important factor determining the proportion of time the birds

spent feeding.

I believe the afternoon feeding peak was correlated with the

optimum time to feed. Several factors contributed to this. Diurnal

temperatures in the central Oregon area reach a maximum in the

afternoon (Figure Z8). Diurnal patterns of aquatic insect emergence

also tend to reach a maximum in the afternoon (e.g. Corbet, 1966)(e. g.

Figure Z8). Further, insects generally are more active at warmer

temperatures (Chapman, 1969), which should increase the ease of

capture by avocets. Similar responses have been observed in other

species which feed on insects; Willow Warblers (Phylloscopus

trochilus), European Robin (Erithacus rubecula), Blue Tits (Parus

caeruleus), Blackbirds (Turdus merula), White-crowned Sparrows,

and Long-billed Marsh Wrens have been shown to have afternoon

feeding maxima (Kuusisto, 1941; Lees, 1948; Morton, 1967; Verner,

1965). The morning foraging peak is not as common, although

Morton (1967) found this peak for White-crowned Sparrows on the

1 1 2

wintering grounds, and Hintz and Dyer (19 70) found the same situa-

tion in breeding Red-winged Blackbirds. It appears that many pas-

serines during the breeding season spend the morning hours in mating

activities (Verner, 1965; Schartz and Zimmerman, 19 71). The ability

to do this requires that the birds be able to store enough energy the

day before to last them through the night and the following morning.

The present evidence suggests that avocets may not be very efficient

in storing enough energy to last through the morning. Also, their

mating activities do not require as much time during the morning

hour s.

The other major feature of the diurnal activity pattern was the

resting phase. A resting or inactive period occurring sometime

during the day occurs in many species of birds. The timing of the

rest period varies, but for most it comes shortly after noon (Palm-

gren, 1949; Aschoff, 1966). However, avocet's inactive period

occurred in mid to late morning. This pattern is in contrast to

the generalization that larger species might be expected to have

afternoon rest periods because they need to feed less (Gibb, 1960).

There has been a great deal of speculation and study to determine why

various species tend to be inactive at a certain time of day. Such

things as avoidance of high mid-day temperatures, low humidities

and so on have been used as explanations.

One assumes, as with the rest of the diurnal time budget, that

1 1 3

the timing of the rest period is subject to natural selection and is

adaptive. In avocets, foraging took the major part of the early

morning as well as most of the afternoon, leaving little time for

resting during these periods. By resting in mid-morning the birds

did not interfere with times when feeding was necessary or environ-

mental conditions were optimal for foraging. Schartz and Zimmerman

(1971) have found a similar resting pattern for the male Dickcissel.

It may be that insectivorous species tend to rest in the morning in

order to take advantage of afternoon insect activity.

Foraging and resting appear to be the dominant activities in con-

trolling the form of the diurnal activity budget. How are other activi-

ties organized in time in response? The major trend is for most

activities to take about the same amount of time in each period of

the day (Figure 27).

Sexual Aspects of the Time Budget

Male and female avocets are similar both morphologically and

behaviorally. This is reflected by the absence of any major differ-

ences between the two sexes in both the seasonal and diurnal time

budgets. Both the behavioral and ecological relationships between

the sexes are probably important in determining the reasons for

the lack of sexual divergence.

114

Several situations may promote the occurrence of sexual

divergence. They include intersexual competition for food and mate

selection (Selander, 1966). The latter is most often seen for poly-

gamous or lek social systems. The opportunity for sexual divergence

due to intersexual competition depends upon the habitat being suffici-

ently complex to be subdivided (Selander, 1966). Avocets may sub-

divide food resources between the sexes by a divergence of bill shape

(Hamilton, 1969). The simplicity of the habitat in which avocets feed

may limit the possibilities for further morphological divergence.

Hamilton has found that both sexes feed in the same depth water, but

I have observed that male and females may feed in somewhat different

areas. A spatial divergence would not be reflected in either morph-

ology or in the time budget.

Considering the extended incubation period of avocets (24 days)

and the necessity for the eggs to be covered almost continually, t!-ere.

is little time for males to court or attend more than one female.

This has possibly reduced selective pressure associated with mate

selection. Also mate selection is not associated with a territory and

neither sex has behavioral patterns which might be used to advertise

a territory. Waders which do use the territory for mate selection

have special behavior patterns for courting females and proclaiming

the territory. Due to the avocet's conspicuousness in the marsh

11 5

habitat they probably do not require special advertising displays.

The simplicity of the habitat, the avocet's particular mating system,

the necessity of covering the eggs almost continuously, and the ex-

tended parental care stage (30+ days) probably account for the general

similarities in the seasonal and diurnal time budgets of the sexes.

This study of the temporal organization of the avocet's behav-

ioral activities in time has illustrated the importance of the time

dimension toward an understanding of both the behavior and ecology

of this species. Further, the relationship between time and energy

appears to be very important in determining the way time utilization

is organized.

The results of this study suggest several lines for further in-

vestigation. I have attempted to indicate the manner in which energy

requirements influence the structure of a time budget. Indeed, as

Collias et al. (19 71) have pointed out, time studies have limited value

unless they can be quantitatively related to behavioral energetics

through metabolic measures. Therefore a logical extension of a time

budget study is an investigation of avocet energy requirements, in-

cluding food abundance and availability.

Another area of considerable interest is the relationship between

the sexes, particularly as it relates to niche subdivision. It is pos-

sible that each sex utilizes the habitat differently, but in a way which

is not reflected in time budget differences. Perhaps a time-space

116

analysis considering how the sexes subdivide the habitat would

elucidate sexual differences, if any are present.

11 7

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Baldwin, E. M. 1964. Geology of Oregon. 2d ed. Eugene, Univer-sity of Oregon Coop. 165 p.

Bent, A. C. 1927. Life histories of North American shorebirds.Smithsonian Institution United States National Museum Bulletinno. 142. Part 1. 420 p.

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Corbet, P. S. 1966. Diel periodicities of emergence and ovipositionin riverine Trichoptera. The Canadian Entomologist 9 8: 1025-1034.

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El-Wailly, A. J. 1966. Energy requirements for egg-laying andincubation in the zebra finch, Taeniopygia castanotis. Condor68 :582 -594.

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Gibson, F . 19 71. The breeding biology of the American avocet incentral Oregon. Condor. [In press]

Hamilton, R. B. 1969. The comparative behavior of the Americanavocet (Recurvirostra americana) and the black-winged stilt(Himantopus himantopus mexicanus). Ph. D. thesis.. Berkeley,University of California. 273 numb. leaves.

Hintz, J. V. and M. I. Dyer. 19 70. Daily rhythm and seasonalchange in the summer diet of adult red-winged blackbirds.Journal of Wildlife Management 34:789-799.

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Kluijver, H. N. 1950. Daily routine of the great tit Parus m. majorL. Ardea 38:99-135.

Kuusisto, P. 1941. Studien fiber die Okologie and Tagesrhytrnik vonPhylloscopus trochilus acredula (L. ) mit besonderer Berack-sichtigung der Brutbiologie. Acta Zoologica Fennica 311:1-120.

Lack, D. 1968. Ecological adaptations for breeding in birds.London, Methuen and Company Ltd. 409 p.

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APPENDICES

1 21

APPENDIX 1. Seasonal Time Budget for all Action Patterns

Action Patternmin.

Stage 1d'

V rni . na in.

Stage 2d

g mi

Feeding 770. 0 34. 3 829. 7 38.5 1944. 2 25.5 1809. 0 23.8Resting 853, 0 37. 5 798. 3 37. 1 265. 2 3. 5 376.0 4.9Bathing 6.7 0 12. 7 . 6 18.7 . 2 31.8 .4Preening 223, 0 9.8 146.3 6.8 764.0 10.0 751. 8 9.9Scratching 10.0 .4 6.9 .3 22.8 3. 1 14.3 . 2Two-wing stretch 2. 5 . 1 0. 7 . 0 5.8 . 1 3.8 0Wing-leg stretch 3. 1 . 1 1.8 . 1 2.3 0 3. 5 0Wingshake 1.7 0 0, 3 0 3. 0 0 4.0 . 1Drinking 0.5 0 5.3 . 2 0. 7 0 0, 3 0Flying 8.3 .4 5.0 . 2 47.8 . 6 49.7 . 6Neck ext ended 0 0 34. 5 1. 6 . 2 0 60.3 .3Precop. preening 33. 5 1. 5 0 0 21. 8 .3 0 0Mount 2.3 . 1 0, 2 0 1. 2 0 0. 2 0Crossed bills 2. 2 . 1 2. 2 . 1 1.8 0 1.8 0Postcop. walk 2. 5 .1 2.3 .1 1.8 0 1, 0 0Crouch 3. 0 . 1 5. 2 , 2 6. 7 . 1 13.5 . 2Single crouch -run 13.8 1.0 7.5 .3 14.2 . 2 21.3 .3Paired crouch-run 14.3 1, 0 12.8 , 6 1.7 0 1. 5 0Pursuit attack 4. 8 . 2 2. 3 . 1 8. 5 . 1 7. 7 . 1Jump attack 6, 7 0 1. 3 . 1 0. 2 0 0 0Retreat 2. 7 . 1 4. 5 . 2 5.0 . 1 7.3 . 1Bowing 4.3 . 2 2.7 . 1 2.8 0 3. 0 0Squ,Ating 0, 3 0 1.0 0 0. 7 0 0, 8 0Pseudosleeping 0, 5 0 0. 7 0 0. 7 0 0, 7 0Parallel walk 1. 3 0 0. 7 0 2, 5 0 1.0 GWingspread 0.2 0 0 0 0 0 0 0Predator chase 3..; 0. 2 2.7 .1 12.0 . 2 19.7 .3Tightrope 0 0 0 0 ,0 0 0Sneak-run 0 0 0 0 1.5 0 3.3 CBr east dipping 0 0 0 0 4. 5 . 1 1. 2 0Alarm circling 0 0 0 0 0. 5 0 3. 8 0Alarm calling 0 0 0 0 6, 8 . 1 3.5 0Ground checking 113.0 5.0 102. 3 4.8 7.3 . 1 3. 5 0Scraping 22, 0 1.0 7.7 .3 0 0 0 0Throwing straws 59.7 2. 6 40. 0 1.8 152. 5 2. 0 68. 5 1.0Nest approach 0.8 0 0 0 109. 3 1.4 70, 2 1. 0Head bobbing 4, 0 . 2 1. 2 0 2.5 0 4.0 0Incubating 0.3 0 0.3 0 6013. 2 39. 6 3477.8 45. 7Upright 94.8 4.1 114.6 5.3 199.3 2.6 275.6 3.7Absent 0 0 0 0 954.5 12.5 549, 0 7.0Brooding 0 0 0 0 0 0 0 0Leading 0 0 0 0 0 0 0 0

Total 2278.3 2153.7 10608.2 7644.4

122

APPENDIX 1. Continued

Action PatternStage 3

0 0Stage 4

min. % min. min.

Feeding 390. 2 32.3 353.8 29.5 707. 7 50.4 622.0 45. 1Resting 103. 2 8.5 126. 2 10.5 422.0 30. 2 425. 2 30.8Bathing 1.0 .1 1.2 .1 0 0 0.3 0Preening 93.2 7.7 113.7 9.5 236.2 16.9 294.3 21.3Scratching 2.7 .2 0.5 0 4.3 .3 2.8 .2Two-wing stretch 0.8 . 1 0. 5 0 2. 7 2 3. 2 . 2Wing-leg stretch 1.5 1 0. 3 0 2. 2 . 2 3. 2 . 2Wingshake 0 0 0 0 1.0 1 1.3 .1Drinking 0 0 0 0 0 0 0.2 0Flying 21.5 .8 18.3 1.5 6.7 .5 6.2 .4Neck extended 0 0 0 0 0 0 0 0Precop, preening 0 0 0 0 0 0 0 0Mount 0 0 0 0 0 0 0 0Crossed bills 0 0 0 0 0 0 0 0Postcop. wall 0 0 0 0 0 0 0 0Crouch 0.7 0 1.2 .1 0.8 1 0.2 0Single crouch-run 7.8 .6 9.3 .8 1. 2 . 1 1.0 1

Paired crouch-run 0 0 0 0 0.2 0 0. 2 0Pursuit attack 10. 5 .9 5.8 .5 0. 7 0 0. 3 0jump attack 0. 3 0 0. 3 0 0 0 0 0P etrcat 1.3 .1 1.5 .1 2.5 .2 2.8 .2Bowing 0.8 .1 0. 5 0 0 0 0. 2 0Squatting 0 0 0 0 0 0 0 0Pseudosleeping 0 0 0 0 0 0 0 0Parallel walk 16.5 1.4 1.0 1 0.3 0 0 0Wingspread 1.2 .1 0.2 0 0 0 0.2 0Predator chase 0 0 0. 2 0 0 0 0 0Tightrope 0 0 0 0 0 0 0 0Sneak-run 0.7 0 0. 3 0 0 0 0 0Breast dipping 0 0 0 0 0 0 0 0Alarm circling 7.8 .6 15. 5 1. 3 0 0 0 0Alarm calling 4.8 .4 3. 5 . 2 0 0 0 0Ground checking 0 0 0 0 0 0 0 0Scraping 0 0 0 0 0 0 0 0Throwing straws 0. 2 0 0 0 0 0 0 0Nest approach 0.8 . 1 0.2 0 0 0 0 0Head bobbing 0 0 0 0 0 0 0 0Incubating 0 0 29.8 2. 5 0 0 0 0Upright 395.5 32.8 367.8 30.6 11.7 .8 16.4 1, 2Absent 12.7 I . 0 54.8 4.6 0 0 0 0Brooding 75.3 6. 2 68.0 5. 7 0 0 0 0Leading 60.2 3.3 17.7 1.5 0 0 0 0

Total 1211.2 1191.3 1400.2 1380.0

1 23

APPENDIX 2. Diurnal Time Budget for all Action Patterns

min.

0600-0800

9/. min,

Time Period, Stage 1

min.

0800-1000

min.

Feeding 99.0 33.0 99.2 33. 1 40.7 7. 1 62.8 11.0Resting 63.7 21. 2 75.0 25, 0 358.7 68.2 401, 3 70, 4Bathing 0.7 . 2 0 0 .0 , 0 0 0Preening 35, 3 11.8 62.5 14. 2 83.7 14, 7 55.0 9. 6Scratching 0, 5 .2 2.8 .9 1.8 .3 1, 1 . . 2Two-wing stretch 0.3 . 1 0. 2 ,1 0.7 .1 0 0Wing- leg stretch 0. 2 . 1 0. 2 . 1 1. 0 , 2 0.8 . 1

Wingshake 0, 2 . 1 0. 2 . 1 0 0 0 0Drinking 0. 2 ,1 0 0 0 0 0. 3 . 1

Flying 1.0 .3 1. 2 .4 1.5 .3 1. 1 . 2Neck extended 0 0 8.7 2.9 0 0 0 0Precop. preening 7.8 2. 6 0 0 0 0 0 0

Mount 1.0 .3 0 0 0 0 0 0

Crossed bills 1.0 .3 1.0 . 3 0 0 0 0Postcop. walk 1.2 .4 1.2 .4 0 0 0 0Crouch 0, 5 .2 0 0 0. 7 ,1 0, 1 0Single crouch-run 1. 5 .5 0.5 . 2 1.3 . 2 1.0 . 2Paired crouch-run 2.3 .8 2.3 .8 2.8 .5 3.0 , 5

Pursuit attack 1.0 . 3 0.5 .2 0 0 0 0Jump attack 0 0 0 0 0.3 . 1 0. 1 0Reheat 0.7 .2 0.7 .2 0.7 .1 0.7 .1Bowing 0 0 0 0 1. 1 .2 1.0 .2Squatting 0 0 0 0 0 0 0 0

Pseudosleeping 0 0 0 0 0 0 0 0Parallel walk 0 0 0 0 0 0 0 0

Wingspread 0 0 0 0 0 0 0 0

Predator chase 0 0 0 0 0 0 0 0Tightrope 0 0 0 0 0 0 0 0Sneak-run 0 0 0 0 0 0 0 0

Breast dipping 0 0 0 0 0 0 0 0Alarm circling 0 0 0 0 0 0 0 0Alarm calling 0 0 0 0 0 0 0 0Ground checking 33.8 11.3 29.8 9.9 23.8 4. 2 20.8 3.7Scraping 5. 2 1.7 3.3 1. 1 3.0 . 5 0. 1 0Throwing straws 18.0 6.0 16.8 5. 6 8.3 .5 0. 3 . 1

Nest approach 0 0 0 0 0 0 0 0

Head bobbing 2. 3 .8 0. 5 . 2 0. 1 0 0 0

Incubating 0.3 ,1 0. 3 . 1 0 , 0 .0 0

Upright 22.4 7.5 13.3 4.4 9.7 1.7 19.9 3.5Absent 0 0 0 0 0 0 0 0

Brooding 0 0 0 0 0 0 0 0

Leading 0 0 0 0 0 0 0 0

Total 300.1 320.2 569.9 569.4

1 24

APPENDIX 2. Continued

ruin.

1000-1200

min.

Time Period, Stage 1

min.

1200-1400

ruin.

Feeding 150.8 38. 7 166.3 42. 6 130. 7 43. 6 144.7 47.8

Resting 104.8 26.9 9. 25 25.0 118.7 39. 6 63. 7 26. 6

Bathing 0 0 0 0 0 0 0 0

Preening 19.1 4.0 25.7 6.6 3.0 1.0 9.0 3.8

Scratching 0.8 .2 1.5 .4 0.1 0.1 0.1 0.1

Two-wing stretch 0.7 .2 0, 8 . 2 0 0 0. 1 . 1

Wing-leg stretch 0. 3 . 1 0.3 . 1 0 0 0.3 . 1

Wingshake 0 0 0 0 0 0 0 0

Drinking 0 0 0 0 0. 1 .1 0 0

Flying 0 0 0 0 0.1 .1 0 0

Neck extended 2.0 .5 1. 3 .3 0 0 0.3 i

Precon. preening 0 0 13.8 3.5 0 0 8.8 3.7Mount 12.8 3.3 0 0 5.0 1.7 0 0

Crossed bills 0. 8 .2 0 0 0. 3 .1 0 0

Postcop. walk 0. 5 .1 0.5 .1 0.3 .1 0. 1 .1Crouch 0. 5 . 1 0.5 . 1 0. 3 . 1 0. 1 . 1

Single crouch-run 0 0 1. 1 .3 0. 5 .2 0. 1 . 1

Paired crouch-run 5.0 1.3 2.5 . 6 1. 1 .4 1. 7 .7Pursuit attack 2. 5 . 6 2.5 . 6 0.7 . 2 0.3 . 1

J7.uulp attack 1. 3 .3 0. 3 . 1 0. 1 . 1 O. 1 . I

Retreat 0 0 0 0 O. 1 . 1 0.5 .2Bowing 0.3 .1 0.7 .2 0.3 .1 1.1 .5Sq:zatting 0.7 . 2 0. 7 . 2 0. 1 ,1 0 0

Ps eudosleeping O. 3 .1 0.3 . 1 0 0 0 0

Ps: ',11e1 walk 0 0 0,1 0 0 0 0 0

Wingspread 0.5 .1 0 0 0 0 0 0

Predator chase 0 0 0 0 0. 1 . 1 0 0

Tightrope 0 0 0 0 0, 5 . 2 0 0

Sneak-run 0 0 0 0 0 0 0 0

Breast dipping 0 0 0 0 0 0 0 0

Alarm circling 0 0 0 0 0 0 0 0

Alarm calling 0 0 0 0 0 0 0 0

Ground checking 0 0 0 0 0 0 0 0

Scraping 22.0 5. 6 21.1 5.4 18.0 6.0 17.3 7. 2

Throwing straws 6.5 1.7 1.5 .4 4.7 1. 6 1.3 . 6

Nest approach 21.5 5. 5 13.3 3.4 7. 1 2.4 9.5 4.0Head bobbing 0 0 0 0 0.8 . 3 0 0

Incubating 1.0 .3 0 0 0 0 0 0

Upright 0 0 0 0 0 0 0 0

Absent 35.1 9. 1 37.4 9. 6 6, 8 2.3 9.8 4. 1

Brooding 0 0 0 0 0 0 0 0

Leading 0 0 0 299. 4 269. 2

Total 389.8 389.7

1 25

APPENDIX 2. Continued

min.

14

%

00-1600

min.

Time Period, Stage 11600-1800

d`min. min.

Feeding 163.0 45.3 180.3 50.1 194.3 53.9 206.5 57.4Resting 102. 3 28.4 108. 1 30. 1 74.8 20.8 52.5 14. 6Bathing S.1 1.4 4.0 1.1 1.0 .3 6.8 1.9Preening 38.7 10.7 40.3 1 1.2 43.0 11.9 38.5 10.2Scratching 3.1 .9 0.5 .1 3.5 1.0 1.8 .5Two-wing stretch 0. 5 .1 0. 5 .1 0.3 . 1 0 0Wing-leg stretch 0.8 .2 0. 3 . 1 0.8 .2 0 0Wingshake 0.8 .2 0.5 .1 0.7 .2 0. 1 0Drinking 0 0 0 0 0. 1 0 0. 1 0Flying 2.5 .7 0.7 .2 1.3 .4 0.3 .1Neck extended 0 0 4.8 1.3 0 0 3. 1 .9Precop. prening 4.3 1.2 0 0 3.5 1.0 0 0Mount 0.1 0 0 0 0.1 0 0 0Crossed bills 0. 1 0 0 0 0. 1 0 0. 1 0Postcop. walk 0. 3 .1 0.3 .1 0. 1 0 0. 1 0Crouch 0. 1 0 0.3 . 1 1. 1 .3 1.3 .4Single crouch-run 2. 8 .8 2. 3 .6 2.0 . 6 0.7 .2Paired crouch-run 1.3 .4 1. 1 .3 4.7 1.3 4.1 1.2Pursuit attack 1.3 .4 0.5 . 1 1.0 .3 1.3 .4Jump attack 0 0 0 0 0. 1 0 0.3 .1Retreat 0.1 0 0.3 .1 0.5 .1 0.8 .3Bowing 1.3 .4 0.1 0 1.0 .3 1.0 .3Squatting 0 0 0 0 0 0 0.7 .2Pseudosleeping 0 0 0 0 0.5 . 1 0.5 . 1Parallel walk 0 0 0 0 0.7 .2 0.7 .2Wingspread 0 0 0 0 0 0 0 0Predator chase 0 0 0 0 3.0 .8 2.7 .7Tightrope 0 0 0 0 0 0 0 0Sneak-run 0 0 0 0 0 0 0 0Breast dipping 0 0 0 0 0 0 0 0Alarm circling 0 0 0 0 0 0 0 0Alarm calling 0 0 0 0 0 0 0 0Ground checking 6.7 1.0 6. 1 1.7 8.7 2.4 7.0 1.9Scraping 2.1 .6 1.3 .4 0.5 .1 0 0Throwing straws 4. 1 1.2 0 0 0.5 . 1 0 0Nest approach 0 0 0 0 0 0 0 0Head bobbing 0.5 . 1 0. 7 .2 0 0 0 0Incubating 0 0 0 0 0 0 0 0Upright 10.4 2.9 6.1 1.7 10.5 3.0 28.2 7.9Absent 6.8 1.9 0 0 1.2 .4 0 0Brooding 0 0 0 0 0 0 0 0Leading 0 0 0 0 0 0 0 0

Total 359.1 363.1 359.6 365.5

126

APPENDIX 2, Continued

dmin.

0600-; 0800

min.

Time Period, Stage 2

dmin.0800-1000

min.

Feeding 608.5 28.4 325.8 22.6 266.5 20.2 279.1 21,2Resting 9.5 .7 59.5 4.1 70.8 5.4 62.0 4.7Bathing 5.0 . 3 4.1 . 3 0.7 . 1 1.5 . 1Preening 146.5 10.2 150.0 10.4 304.8 1 1.7 168.5 12.8Scratching 4.5 .3 2.8 . 2 3.3 .3 1.8 . 1Two-wing stretch 0.3 0 0.7 0 1.8 ,1 0.8 . 1Wing-leg stretch 0 0 0.1 0 0.8 ,1 0.5 0Wingshake 0.8 . 1 1.0 ,1 0 0 0.5 0Drinking 0 0 0 0 0.3 0 0,1 0Flying 8.5 .6 7.5 .5 9.7 .7 11.5 .9Neck extended 0 0 16.1 1.1 0 0 2.0 . 2Pr econ. preening 15.7 1.1 0 0 1.8 ,1 0 0Mount 0.7 0 0 0 0.1 0 0.1 0Crossed bills 0.7 0 0.5 0 0.1 0 0.1 0Postcop. walk 0.8 ,1 0.7 0 0.1 0 0.1 0Crouch 2.0 . 1 4.0 , 3 0.5 0 1.0 .1Single crouch-run 4.7 .3 4.3 , 3 1.0 . 1 4.3 .3Paired crouch-run 0.7 0 0.5 0 0.1 0 0.1 0Palsuit attack 3.0 . 2 1.7 . 1 0.1 0 1.0 . 1juinp at-rs=_ck 0.1 0 0.1 0 1.3 . 1 0.1 0Retreat 1.7 .1 1.5 . 1 0.5 0 1.0 . 1Bowing 1.5 I 0.7 0 0.1 0 1.0 . 1Squatting 0,1 0 0 0 0.1 0 0 0Pseu.dosleeping 0.5 0 0 0 0 0 0 0Parallel walk 0.1 0 0 0 1.7 . 1 0 0Wingspread 0 0 0 0 0 0 0 0Predator chase 1.8 .1 3.3 .2 3.5 .3 10.8 .8Tightrope 0 0 0 0 0 0 0 0Sneak-run 0 0 0.1 0 0.3 0 1.0 ,1Breast dipping 0 0 0 0 0 0 0 0Alarm circling 0.3 0 0.1 0 0 0 2.3 . 2Alarm calling 0 0 0.1 0 4.5 . 3 1.1 . 1Ground checking 0 0 0 0 0 0 0 0Scraping 0 0 0.1 0 0.1 0 0 0Throwing straws 46.0 3.2 11.7 .8 39,7 3.0 15.5 1.2Nest approach 20.3 1.4 11.7 , 8 20.0 1.5 23.1 1,8Head bobbing 0.8 .1 0.5 0 0.3 0 0.8 . 1Incubating 449.7 31.2 723.3 50.3 539.8 40.9 607.0 46.0Upright 42.8 3.0 35.8 2.5 39.2 3.0 101.2 7.7Absent 261.8 18.2 70.3 4.9 155.5 11.8 19.1 1.5Brooding 0 0 0 0 0 0 0 0Leading 0 0 0 0 0 0 0 0

Total 1639.4 1438.6 1969.1 1319.0

127

APPENDIX 2. Continued

min.

1000 -1200

% min.

Time Period, Stage 2

c/i min.

1200-1400

ruin.

Feeding 386.0 23.6 376.5 23.2 383.5 36.5 326.0 31, 0Resting 57.5 3.5 157.7 9.7 7.7 .7 9.0 .9Bathing 0.8 . 1 3.7 . 2 0.5 0 0.8 . 1Preening 144.8 8.9 138.0 8.5 95. 1 9. 1 68, 0 6.5Scratching 5. 1 .3 2.3 .1 2.3 .2 2. 1 . 2Two-wing stretch 1.3 . 1 0.3 0 1.0 . 1 0.3 0Wing-leg stretch 0.3 0 1.5 . 1 0.5 0 0. 1 0Wingshake 0. 1 0 I . 0 .1 0. 1 0 0. 1 0Drinking 0 0 0 0 0.3 0 0 0Flying 10.1 .6 11.0 .7 5.1 .5 4.7 .4Neck extended 0 0 1.8 . 1 0 0 0 0Precop. preening 3.3 .2 0 0 0 0 0 0Mount 0.7 0 0 0 0 0 0 0Crossed sills 0.7 0 0.8 .1 0 0 0 0Postcop. walk 0.7 0 0. 1 0 0 0 0 0Crouch 0.1 0 4.7 .3 0.7 .1 1.1 .1Single crouch-run 1.8 . 1 1.7 . 1 0.8 . 1 4.3 .4Paired crouch-run 0, 5 0 0. 5 0 0. 5 0 0. 5 0Purs_iit attack 0. 1 0 1.8 . 1 2. I . 2 1.8 .2Jump attack 0 0 0 0 0 0 0 0Retreat 1. 1 . 1 2.1 .1 0. 1 .0 1. 1 . 1Bowing 0.3 0 0. 1 0 0.8 . 1 1. 1Squatting 0.3 0 0.7 0 0 0 0. 1 0Ps euslosleeping 0.1 0 0. 7 0 0 0 0 0Parallel walk 0 0 0 0 0 0 1.0 .1Wingspread 0 0 0 0 0 0 0 0Predator chase 3. 1 .2 2. 1 . 1 1 .0 . 1 0.8 .1Tightrope 0 0 0 0 0 0 0 0Sneak-run 0 0 0 0 0.5 0 1.0 .1Breast dipping 0 0 0 0 4.5 .4 1, 1 , 1Alarm circling 0 0 0. 1 0 0 0 1. 1 .1Alarm calling 0.3 0 0.8 0 1.3 . 1 0.7 . 1Ground checking 7.3 .5 3. 5 . 2 0 0 0 0Scraping 0.3 0 0 0 0 0 0 0Throwing straws 42.0 2. 6 14.3 .9 18. 1 1. 7 21.3 2.0Nest approach 18.7 1. 2 12.7 .8 23.0 2. 2 10.3 1.1Head bobbing 0. 5 0 2, 0 .1 0, 8 .1 0, 5 0Incubating 709.0 43.8 902.8 43.4 390.1 37.2 516.3 49. 2Upright 32.6 2.0 63.6 3.9 28. 6 2.7 21.2 2. 1Absent 193.3 11.9 110.7 6.8 80.3 7.7 51.7 4.9Brooding 0 0 0 0 0 0 0 0Leading 0 0 0 0 0 0 0 0

Total 1622.8 1619.6 1049.3 1048.1

1 28

APPENDIX 2. Continued

min.

1400-1600cf` .mm.

Time Period, Stage 2

cf`min.

1600-1800

min.

Feeding 300. 1 23.3 342.8 26. 6 603.5 22. 6 158.7 17. 6Resting 65.7 5. 1 66.1 5. 1 54.0 6.0 33.3 3.7Bathing 10.3 .8 15.3 1. 2 1.3 . 1 6.3 .7Preening 114.0 8.8 164.0 12.8 108.7 1 2. 1 62.5 6.9Scratching 4.8 .4 3.7 .3 2.7 .3 1.0 ./Two -wing stretch 1. 1 . 1 1.0 . 1 0. 1 0 0. 5 . 1Wing-leg stretch 0 0 1. 1 . 1 0.7 1 0 0Wingshake 1.7 .1 0.7 . 1 0. 1 0 0. 7 ,1Drinking 0 0 0. 1 0 0 0 0 0Flying 8. 1 . 6 10.3 .8 6, 1 . 7 4.7 .5Neck extended 0 0 0.3 0 0 0 0 0Precop. preening 1.0 .1 0 0 0 0 0 0Mount 0.1 0 0 0 0 0 0 0Crossed bills 0. 1 0 0. 1 0 0. 1 0 0,1 0Postcop. walk 0. 1 0 0 0 0 0 0 0Crouch 1. 1 ,1 1.0 .1 2. 1 .2 1.7 .2Single crouch-run 2.7 . 2 3.8 .3 3. 1 .4 2.8 .3Paired crouch-run 0. 1 0 0. 1 0 0.7 .1 0.7 . 1Pursuit attack 1.0 . 1 0. 1 0 2. 0 . 2 1. 1 . 1jump attack 0 0 0 0 0. 1 0 0 0Retreat 0 8 .1 1. 1 .1 0.7 .1 0.3 0Bowing 0 0 0 0 0 0 0 0Squatting 0 0 0 0 0 0 0 0Pseudosleeping 0 0 0 0 0 0 0 0Parallel walk 0.3 0 0 0 0.3 0 0 0Wingspread 0 0 0 0 0 0 0 0Predator chase 1. 5 . 1 1. 1 . 1 1.0 . 1 1.3 . 1Tightrope 0 0 0 0 0 0 0 0Sneak -run 0. 7 . 1 0.8 . 1 0 0 0.5 .1Breast dipping 0 0 0 0 0 0 0 0Alarm circling 0. 1 0 0 0 0 0 0 0Alarm calling 0.5 0 0. 3 0 0. 1 0 0.3 0Ground checking 0 0 0 0 0 0 0 0Scraping 0 0 0 0 0 0 0 0Throwing straws 6.7 . 5 3.3 .3 0 0 2. 3 ,3Nest approach 18.3 1.4 7.1 . 6 9.0 1.0 5. 1 .6Head bobbing 0 0 0 0 0 0 0. 1 0Incubating 617.7 47.9 495. 1 38.4 306.8 34. 1 433. 1 48. 1Upright 35. 7 2.7 23.3 1.8 20. 2 2. 2 30.3 3.3Absent 94.3 7.3 145.0 1 1. 2 175.8 19.5 152.1 16.9Brooding 0 0 0 0 0 0 0 0Leading 0 0 0 0 0 0 0 0

Total 1288.6 1287.6 1299.2 899.5

129

APPENDIX 2. Continued

min.

Time Period, Stage 30600-080 0

min. min.

0800-1000

min.

Feeding 97. 5 40. 6 74. 1 30, 9 0 0 0 0Resting 18.0 7, 5 0 0 2.7 8.9 0 0Bathing 0 0 0 0 0 0 0 0Preening 22.3 9.3 39.3 16.4 6.5 21.7 3. 1 10. 6Scratching 0. 1 ,1 0 0 0. 1 . 6 0 0Two-wing stretch 0 0 0 0 0 0 0 0Wing-leg stretch 0 0 0. 1 . 1 0 0 0 0Wingshake 0 0 0 0 0 0 0 0Drinking 0 0 0 0 0 0 0 0Flying 5.7 2.4 5.8 2.4 0. 1 . 6 0.7 2, 2Neck extended 0 0 0 0 0 0 0 0Precop. preening 0 0 0 0 0 0 0 0Mount 0 0 0 0 0 0 0 0Crossed bills 0 0 0 0 0 0 0 0Postcop. walk 0 0 0 0 0 0 0 0Crouch 0. 3 ,1 0 0 0 0 0. 7 2.2Single crouch-run 2. 7 1. 1 2, 0 .8 0 0 0. 1 . 6Paired crouch-run 0 0 0 0 0 0 0 0Pursuit attackck 1. 5 . 6 0.8 .3 0. 5 1. 7 0. 1 .6Jump attack 0, 1 .1 0, 3 ,1 0 0 0 0Retreat 0, 3 .1 0 0 0 0 0 0Bowing 0. 1 .1 0. 1 .1 0 0 0 0Squatting 0 0 0 0 0 0 0 0Pseudosleeping 0 0 0 0 0 0 0 0Parallel 1,t7.1.11z. 0. 1 . 1 0, 1 . 1 0 0 0 0Wingspread 0 0 0 0 0 0 0 0Predator chase 0 0 0 0 0 0 0 0Tightrope 0 0 0 0 0 0 0 0Sneak-run 0.5 .2 0 0 0 0 0.3 1. 1Breast dipping 0 0 0 0 0 0 0 0Alarm circling 1.0 .4 0, 7 .3 0 0 0 0Alarm calling 0 0 0 0 0 0 0 0Ground checking 0 0 0 0 0 0 0 0Scraping 0 0 0 0 0 0 0 0Throwing straws 0, 1 .1 0 0 0 0 0 0Nest approach 0 0 0 0 0 0 0 0Head bobbing 0 0 0 0 0 0 0 0Incubating 0 0 0 0 0 0 0 0Upright 51.6 21.5 94.8 39.5 11, 5 37.4 3.5 11.7Absent 0 0 13.8 5.8 6.0 20.0 21.3 71. 1Brooding 37.3 15.6 7. 1 3, 0 0 0 0 0Leading 0, 3 . 1 0, 5 .2 2.5 8.3 0 0

Total 239.5 239.7 29.9 29.8

130

APPENDIX 2. Continued

min.

10001200d min.

Time Period, Stage 3

min.

1200.1400d' min.

Feeding 49.5 23. 6 77. 1 36. 7 52.8 35.2 40.7 27. 1

Resting 35,5 16.9 35.8 17. 1 0.5 .3 14.5 9.7

Bathing 0 0 0 0 1.0 .7 0 0

Preening 12.8 6.1 7.0 3.3 3.7 2.4 4.7 3.1

Scratching 0.5 .2 0 0 0 0 0 0

Two-wing stretch 0. 1 ./ 0. 1 . 1 0. 3 .2 0. 3 .2

Wing-leg stretch 0 0 0 0 0 0 0. 1 _ . 1

Wingshake 0 0 0 0 0 0 0 0

Drinking 0 0 0 0 0 0 0 0

F lying 2.8 1.3 2.5 1. 2 1.8 1. 2 0.8 .6

Neck extended 0 0 0 0 0 0 0 0

Precop. preening 0 0 0 0 0 0 0 0

Mount 0 0 0 0 0 0 0 0

Crossed bills 0 0 0 0 0 0 0 0

Postcop. walk 0 0 0 0 0 0 0 0

Crouch 0 0 0.3 .2 0 0 0 0

Single crouch-run 1. 1 . 6 0.7 .3 2.0 1.3 1.8 1. 2

Paired crouch-run 0 0 0 0 0 0 0 0

Pursuit attack 1,8 .9 1. 1 .6 2.7 1.8 2.0 1.3

Jump attack 0 0 0 0 0 0 0 0

Retreat 0.1 .1 0 0 0.3 .2 0 0

Bowing 0. 1 .1 0.3 .2 0. 3 .2 0 0

Sci :luting 0 0 0 0 0 0 0 0

Pseudosleeping 0 0 0 0 0 0 0 0

Parallel walk 0 0 0. 1 .1 1.3 .9 0 0

Wingspread 0. 5 .2 0 0 0, 3 . 2 0 0

Predator chase 0 0 0. 1 .1 0 0 0 0

Tightrope 0 0 0 0 0 0 0 0

Sneak-run 0 0 0 0 0 0 0 0

Breast dipping 0 0 0 0 0 0 0 0

Alarm circling 2. 5 1. 2 12. 5 6.0 1. 7 1. 1 0 0

Alarm calling 0 0 0 0 0.7 .4 2.5 1. 7

Ground checking 0 0 0 0 0 0 0 0

Scraping 0 0 0 0 0 0 0 0

Throwing straws 0 0 0 0 0 0 0 0

Nest approach 0.8 .4 0. 1 .1 0 0 0 0

Head bobbing 0 0 0 0 0 0 0 0

Incubating 0 0 29.8 14.2 0 0 0 0

Upright 81.8 29.0 37.0 17.8 72.7 48.4 61.6 41.1

Absent 0 0 0 0 0 0 0 0

Brooding 0.8 .4 2.3 1.1 4.5 3.0 17.5 11.7

Leading 18.7 8.9 2.7 1.3 3,3 2.2 3.3 2.2

Total 209.4 208.5 149.9 149.8

131

APPENDIX 2. Continued

mm.

1400-1600

ox,.

Time Period, Stage 3

min.

1600-1800

min.

Feeding 19.5 32.5 21.7 36. 1 170.8 33.5 140. 1 27.5Resting 2. 5 4.2 2. 1 3. 6 44.0 8. 6 73.7 14.4Bathing 0 0 0 0 0 0 1.1 .2Preening 4. 1 6.9 8. 1 13. 6 43.7 8. 6 51.3 10. 1Scratching 0. 1 .3 0 0 1.3 .3 0.5 . 1Two-wing stretch 0 0 0 0 0.3 . 1 0 0Wing-leg stretch 0 0 0 0 1. 5 .3 0 0Wingshake 0 0 0 0 0 0 0 0Drinking 0 0 0 0 0 0 0 0Flying 0.7 1. 1 0, 5 .8 7.5 1.5 8.0 1.6Neck extended 0 0 0 0 0 0 0 0Precop. preening 0 0 0 0 0 0 0 0Mount 0 0 0 0 0 0 0 0Crossed bills 0 0 0 0 0 0 0 0Postcop. walk 0 0 0 0 0 0 0 0Crouch 0.3 . 6 0 0 0 0 0. 1 0Single crouch-run 0. 1 . 3 0 0 1.8 .4 4.7 .9Paired crouch-rum 0 0 0 0 0 0 0 0P IlfEIJ it attack 2.0 3. 3 0. 1 .3 2.0 .4 1.5 .3rump attack 0 0 0 0 0 0 0 0Retreat 0 0 0 0 0.5 . 1 1.5 .3Bowing 0, 1 3 0 0 0 0 0 0Scatting 0 0 0 0 0 0 0 0Pseadosleeping 0 0 0 0 0 0 0 0Parallel walk 0 0 0 0 14.8 2.9 0. 7 . 1Wingspread 0 0 0 0 0. 3 .1 0. 1 0Predator chase 0 0 0 0 0 0 0 0Tightrope 0 0 0 0 0 0 0 0Sneak-run 0. 1 .3 0 0 0 0 0 0Breast dipping 0 0 0 0 0 0 0 0Alarm circling 0 0 0 0 1.7 .5 1.3 .5Alarm calling 0 0 0 0 4. 1 .8 0 0Ground checking 0 0 0 0 0 0 0 0Scraping 0 0 0 0 0 0 0 0Throwing straws 0 0 0 0 0 0 0 0Nest approach 0 0 0 0 0 0 0 0He ad bobbing 0 0 0 0 0 0 0 0Incubating 0 0 0 0 0 0 0 0Upright 29.8 49.7 22.6 37.8 147.9 29.0 147.3 28.9Absent 0 0 3. 1 5.3 6.7 1.3 16.5 3. 2Brooding 0 0 0 0 32. 7 6.4 41.0 8.0Leading 0.3 .6 1.5 2.5 15.0 2.9 9.7 1.9

Total 60. 0 60. 0 496. 6 499. 1

132

APPENDIX 2. Continued

min.

0600-0800

min.d

mm.

Time Period, Stage 4

min.

0800-1000

min.

Feeding 68.7 76.3 68.1 75.7 111.1 37.2 95.7 31.9

Resting 17.3 19.3 18.5 20.6 95.0 31.7 128.1 42.7

Bathing 0 0 0 0 0 0 0 0

Preening 1.3 1.5 0.1 .2 87.1 29.1 71.1 23.7

Scratching 0.1 .2 0 0 1.7 .6 0.7 .2

Two-wing stretch 0.5 .6 0.8 .9 0.7 .2 0.3 .1

Wing-leg stretch 0 0 0 0 0.5 . 2 1.1 .4

Wingshake 0 0 0 0 0 0 0 0

Drinking 0 0 0 0 0 0 0 0

Flying 1.1 1.3 1.0 1.1 1 . 0 .3 1.0 .3

Neck extended 0 0 0 0 0 0 0 0

Precop. preening 0 0 0 0 0 0 0 0

Mount 0 0 0 0 0 0 0 0

Crossed bills 0 0 0 0 0 0 0 0

Postcop. walk 0 0 0 0 0 0 0 0

Crouch 0 0 0 0 0 0 0 0

Single crouch-run 0 0 0 0 0 0 0,5 .2

Paired crouch-run 0 0 0 0 0 0 0 0

Purs'..,.it attack 0 0 0 0 0 0 0 0

Jump p attack 0 0 0 0 0 0 0 0

Retreat 0 0 0 0 0.7 .2 0.7 2

Bowing 0 0 0 0 0 0 0 0

Sq.Aatting 0 0 0 0 0 0 0 0

Pseadosleeping 0 0 0 0 0 0 0 0

Parallel walk 0 0 0 0 0 0 0 0

Wingspread 0 0 0 0 0 0 0 0

Predator chase 0 0 0 0 0 0 0 0

Tightrope 0 0 0 0 0 0 0 0

Sneak-run 0 0 0 0 0 0 0 0

Breast dipping 0 0 0 0 0 0 0 0

Alarm circling 0 0 0 0 0 0 0 0

Alarm calling 0 0 0 0 0 0 0 0

Ground checking 0 0 0 0 0 0 0 0

Scraping 0 0 0 0 0 0 0 0

Throwing straws 0 0 0 0 0 0 0 0

Nest approach 0 0 0 0 0 0 0 0

Head bobbing 0 0 0 0 0 0 0 0

Incubating 0 0 0 0 0 0 0 0

Upright 1.6 1.0 1.5 1.5 1.5 . 6 1.3 .2

Absent 0 0 0 0 0 0 0 0

Brooding 0 0 0 0 0 0 0 0

Leading 0 0 0 0 0 0 0 0

Total 90.6 90.0 299.3 300.5

133

APPENDIX 2. Continued

10001200

min.

Time Period, Stage 4

min.

1200-1400

min.

FeedingRestingBathingPreening

57.0151.1

0

22.7

23.863.0

09.4

62.0128.8

038.7

25.853.7

01 6.1

149. 121.0

0

39.5

71.010.0

017. 2

133.734. 1

038.5

63.716.3

018.3

Scratching 0. 1 .1 0, 3 . 1 0. 5 . 2 0. 5 . 2

Two-wing stretch 0, 3 . 1 0, 3 . 1 0, 3 .2 0, 1 . 1

Wing-leg stretch 0. 1 ,1 0, 5 . 2 0. 1 . 1 0 0

Wingshake 0 0 0 0 0 0 0. 1 . 1

Drinking 0 0 0, 1 . 1 0 0 0 0

Flying 4.0 1.7 3.5 1, 7 0 0 0 0

Neck extended 0 0 0 0 0 0 0 0

Precop. preening 0 0 0 0 0 0 0 0

Mount 0 0 0 0 0 0 0 0

Crossed bills 0 0 0 0 0 0 0 0Postcop. walk 0 0 0 0 0 0 0 0

Crouch 0. 1 .1 0. 1 . 1 0.7 .3 0 0

Single crouch -ran 0, 1 . 1 0 0 0 0 0 0

P a ii° c d crouch-run 0. 1 . 1 0. 1 ,1 0 0 0 0

Purai 1. attack 0. 1 . 1 0. 1 . 1 0 0 0 0

J crnp attack. 0 0 0 0 0 0 0 0

Retreat 0, 3 . 1 0.3 . 1 1.3 . 6 1.7 .8Bowing 0 0 0. 1 .1 0 0 0 0

Seic,:_tting 0 0 0 0 0 0 0Pse.:dosleepinsz 0 0 0 0 0 0 0 0

Parallel walk 0 0 0 0 0 0 0

Wingspread 0 0 0 0 0 0 0 0

Predator chase 0 0 0 0 0 0 0 0

Tightrope 0 0 0 0 0 0 0

Sneak-run 0 0 0 0 0 0 0 0

Breast dipping 0 0 0 0 0 0 0 0

Alarm circling 0 0 0 0 0 0 0 0

Alarm calling 0 0 0 0 0 0 0 0

Ground checking 0 0 0 0 0 0 0 0

Scraping 0 0 0 0 0 0 0 0

Throwing straws 0 0 0 0 0 0 0 0

Nest approach 0 0 0 0 0 0 0, 1 . 1

Head bobbing 0 0 0 0 0 0 0 0

Incubating 6.3 1.5 5, 8 2.0 0.5 .3 0.7 .5Upright 0 0 0 0 0 0 0 0

Abs ent 0 0 0 0 0 0 0 0

Brooding 0 0 0 0 0 0 0 0

Leading 0 0 0 0 0 0 0 0

Total 242.3 240.7 213.0 20S', 3 0

134

APPENDIX 2. Continued

min.

1400::1600

cr

Time Period, Stage 4

cr./D

1600-1800

min.

Feeding 200.7 66.9 172.7 57.6 116.5 48.5 89.8 37.4Resting 56.8 18.9 61.5 20.5 64.0 26.7 54.0 22.5Bathing 0 0 0 0 0 0 0 0

Preening 36.3 12. 1 55.0 18.3 52.5 21.9 90.8 37.8Scratching 0.5 .2 1.0 .3 1.3 .6 0.3 .1l'wo-wing stretch 0. 7 .2 0.5 . 2 0. 1 . 1 1.0 .4Wing-leg stretch 0. 7 .2 1.3 .4 0.7 .3 0. 1 . 1

Wingshake 0.8 .3 0.5 .2 0. 1 .1 0. 7 .3Drinking 0 0 0 0 0 0 0 0

Flying 0.1 .1 0 0 0.3 .1 0.7 .3Neck extended 0 0 0 0 0 0 0 0

Precop, preening 0 0 0 0 0 0 0 0

Mount 0 0 0 0 0 0 0 0

Crossed bills 0 0 0 0 0 0 0 0

Postcop. walk 0 0 0 0 0 0 0 0

Crouch 0 0 0 0 0 0 0 0

Single crouch-run 1.0 .3 0 0 0. 1 . 1 0. 5 .2Paired crouch-run 0 0 0 0 0 0 0 0

F'ris,..it attack 0. 1 .1 0 0 0.3 . 1 0. 1 . 1

Jump attack 0 0 0 0 0 0 0 0

Retreat 0.1 .1 0.1 .1 0 0 0 0

Bowing 0 0 0 0 0 0 0 0

Sciaatting 0 0 0 0 0 0 0 0

Pseudosleeping '') 0 0 0 0 0 0 0

Parallel walk 0 0 0 0 0 0 0 0

Wingspread 0 0 0 0 0. 3 .1 0 0

Predatca. chase 0 0 0 0 0 0 0. 1 .

Tightrope 0 0 0 0 0 0 0 0

Sneak-run 0 0 0 0 0 0 0 0

Breast dipping 0 0 0 0 0 0 0 0

Alarm circling 0 0 0 0 0 0 0 0

Alarm calling 0 0 0 0 0 0 0 0

Ground checking 0 0 0 0 0 0 0 0

Scraping 0 0 0 0 0 0 0 0

Throwing straws 0 0 0 0 0 0 0 0

Nest approach 0 0 0 0 0 0 0 0

Head bobbing 0 0 0 0 0. 5 . 2 0 0

Incubating 0 0 0 0 0 0 0 0

Upright 2.1 .7 7.0 2.3 3.0 1.3 1.7 .7Absent 0 0 0 0 0 0 0 0

Brooding 0 0 0 0 0 0 0 0

Leading 0 0 0 0 0 0 0 0

Total 299.9 299.9 239.7 239.4

APPENDIX 3. Seasonal Time Radget with Categories of Behavior, Sexes Combined

Stage 1min.

Stage 2nin.

Stage 3 Stage 4rn

Feeding 1599.7 36. 4 3753.2 23.1 744.0 30.9 1329, 7 47.7

Restin g 1651.3 37. 3 641.2 4. 2 229.4 9. 5 847. 2 30. 5

Preening 3 69.3 8.3 .515.8 10.00 206.9 8. 6 530. 5 19. 1

Other maint.activities

52.2 .6 1 10. 0 .6 8.5 .3 21.2 .7

Mating 45.2 1.8 90.1 .3 0 0 0 CI

Aggression 1 54. 6 2.1 99.8 .6 58.9 2.4 10.4 .3

Diversionary 6.2 .15 67.6 .35 32.8 1. 4 0 0

Nest Building 309.5 7. 7 411.3 1, 2 1. 2 0 0 0

Incubation 0. 6 0 9491.0 43.5 29.8 0 0 0

Upright 209.4 4.7 4 74.9 3. 2 762.5 31.7 28.1 0.9

Parental 0 0 0 0 221.2 8.4 -0 0

Absent 0 0 1503.5 9.8 67.5 2.8 0 0

Total 4298.0 18199.4 2362.7 2767. 1

APPENDIX 4. Seasonal Time Budget with Categories of Behavior

Stage 1

min. min, min.

Stage 2

min.

Stage 3

Feeding 770.0 34.3 829.7 38, 5 1944, 2 25.8 1809.0 23,8 390.2 32.3 353.8 29. 5

Resting 853.0 37.5 798.3 37. 1 265, 2 3.5 376.0 4.9 103. 2 8. 5 126. 2 10.5

Preening 223.0 9.8 146.3 6.8 764,0 10.0 751.8 9.9 93.2 7,7 113.7 9.5

Other maint.activities

24.5 0. 6 27.7 1, 2 53.3 . 6 57.7 .7 6.0 0. 5 2.5 0. 1

Mating 40.5 1.8 4.7 1.8 26.8 .3 63.3 .3 0 0 0 0

Aggression 115.9 2. 6 38.7 1. i 43.0 . 5 56.8 .7 39. 1 3. 2 19.8 1. 6

Diversionary 3. 5 0. 2 2.7 0. 1 32. 6 .4 35.0 . 3 13. 3 1. 0 19. 5 1. 5

Nest Building 195.5 8. 6 1 14.0 6.9 269. 1 3. 5 142.2 2. 0 1.0 O. 1 0. 2 0

Incubation 0.3 0 0.3 0 6013.2 39.6 3477.8 45.7 0 0 29.8 2.5

Up right 94.8 4. 1 114.6 5. 3 1 99. 3 2. 6 275. 6 3. 7 395.5 32.8 367.0 30. 6

Parental 0 0 0 0 0 0 0 0 135.5 9, 5 85.7 7. 2

Absent 0 0 0 0 954.5 12, 5 549.0 7.0 12.7 1, 0 54.8 4. 6

Total 2321.0 2076.7 10565.2 75942.0 1189.7 1173.0

Stage 4

dmin. min.

Feeding707. 7 50.4 622.0 45. 1

Resting422.0 30.2 425. 2 30.8

Preening236.2 16.9 294.3 21. 3

Other maint. activities 10. 2 0.8 11.0 0. 7

Mating 0 0 0 0

Aggression 5.7 0.4 4. 2 0. 3

Diversionary0 0 0 0

Nest Building 0 0 0 0

Incubation0 0 0 0

Upright11.7 0.8 16.4 1. 2

Parental0 0 0 0

Absent0 0 0 0

Total1333. 5 1373. 6

APPENDIX 5. Diurnal Time Budget with Categories of Behavior; Sexes Combined

Category

0600-0800 0800-1000

TIME PERIOD

1000-1200 1200-1400

min. min.

1400-1600

min.

1600-1860

min. CA

Stage 1Feeding 198. 0 33. 1 103.5 9.0 317. 1 40.6 245.4 45.7 343.3 47.7 400.8 55. 6

Resting 138. 6 23. 1 790.0 69.3 202. 3 25.9 182.5 33. 1 210.4 29. 2 127.3 17. 7

Preening 97.8 13.0 138.7 12.2 44.8 1 3. 8 12.0 2.4 79.0 10.9 81.5 11.3

Other maint.activities

5.3 1.0 5.8 0, 5 4. 6 0. 6 1.3 0.3 16. 3 2. 1 15. 5 2. 1

Mating 21.8 3.6 0 0 29.3 3.7 15.1 2.9 10.3 1.4 7.5 1.0

Aggression 10.0 1.7 13.0 1. 1 19.0 2.4 7.3 1.5 13.7 1. 6 23.5 3.3

Diversionary0 0 0 0 0 0 0.5 0. 1 0 0 5.8 0. 8

Nest Building 107.0 17.8 56.4 5.0 89.3 11.0 58.8 11, 0 20.5 5.8 16.7 2. 2

Incubation 0. 7 0. 1 0 0 0 0 0 0 0 0 0 0

Upright 35, 4 5.9 29.7 2. 6 70.4 9.3 16.6 3. 2 16.4 2.3 13.3 5.4

Parental 0 0 0 0 0 0 0 0 0 0 0 0

Absent 0 0 0 0 0 0 0 0 0 0 0 0

Total 614.6 1137.1 776.8 539.5 716.7 693.2

Stage 2Feeding 934.3 25.5 546.6 20.7 1062.5 23.4 709.5 33.8 642.9 25.0 762.2 20. 1

Resting 68.0 2.4 1328 4..9 215. 2 6. 6 16.7 0. 8 131, 8 5. 1 87. 3 6.4

Preening 296.5 10.3 473.3 12.2 282.8 8.7 163.1 7.8 278.8 10.8 171, 2 9.5

Other maint.activities

19.5 0.6 12.3 0.4 16. 6 0.5 8.5 0.3 35. 1 1.6 13. 5 0. 8

Mating 35.1 1.2 4.8 0. 2 8. 1 0.2 0 0 2. 2 0. 1 0.2 0

Aggression 27. 3 0.8 14.4 0, 5 17.0 0.4 16.4 0. 8 12.4 0. 5 15.8 0. S

Diversionary 5.9 0. 2 23.6 0.9 6. 6 0. 2 12. 1 0. 6 5, 1 0. 2 3. 2 0. 2

Nest Building 89.6 3. 1 99.6 7.6 98.8 3. 1 73.8 3. 5 35.5 1.4 16.5 1.0

Incubation 1173.0 40.8 1146.8 43.4 1411.8 43.6 906.4 43. 2 /112.8 43.2 739.9 41. 1

Upright 78, 6 2.8 123.8 5. 3 96.4 2.9 50.0 2.4 59.0 2. 2 50.3 2. 7

Parental 0 0 0 0 0 0 0 0 0 0 0 0

Absent 332,1 11, 6 174.6 6. 6 9, 4 132.0 6.3 239.3 9. 2 327.9 18. 2

Total 3060, 9 2752.6

_304.03213. 3 2088.5 2554.9 2188.0

APPENDIX 5. ContinuedTIME PERIOD

0600-0800 0800-1000 100-1200 1200-1400 1400-1600 1600-1800

Category min. min. min. min. min. min. %

Stage 3Feeding 171.6 35.7 0 0 126.6 30.2 93.5 31.2 41.2 34.3 310.9 30, 5

Resting 18.0 3.8 2.7 4.9 71.3 17.0 15.0 5.0 4.6 3.9 117.7 11.5

Preening 61.6 12.8 9.6 16.2 19.8 4.7 8.4 2.8 12.2 10.2 95.0 9.4

Other maint.activities

0.2 0. 1 0. 1 0.3 0.8 0, 2 1.8 0.6 0. 1 0.2 4.8 0. 5

Mating 0 0 0 0 0.1 0. 1 0 0 0 0 0 0

Aggression 8.8 1.8 1.5 2. 6 6.5 1. 6 10.8 3. 6 2.8 2.4 28.2 2.8

Diversionary 2.2 0.4 0.3 0. 6 15.2 3 . 6 4.8 1. 6 O. 1 0. 2 9. 1 0.9

Nest Building O. 1 0. 1 0 0 0.9 0. 3 0 0 0 0 0 0

Incubation 0 0 0 0 29, 8 7. 1 0 0 0 0 0 0

Upright 146.5 30.5 15.0 25.0 118.8 28.3 134.4 4.8 52.5 43.8 295.3 29.0

Parental 45.4 9.4 3. 5 4. 6 24.5 5.8 28.6 9. 6 1.8 1.6 98.4 9. 6

Absent 13.8 2.9 27.3 45.5 0 0 0 0 3. 1 2. 6 23.2 2. 2

Total 468 . 2 60.0 414.3 297.3 118.4 982. 6

Stage 4Feeding 136.8 76.0 206.8 49.6 119.0 24.8 282.8 67.4 373.4 62.4 206.3 42.9

Resting 35.8 20.0 123.1 37.2 279.9 54.8 55.1 13.2 118.3 19.2 118.0 24.6

Preening 1.4 1.8 158.2 26.4 61.4 12.3 78.0 17.8 91.3 15.2 143.3 29.8

Other maint.activities

1.5 0.8 4.9 0.8 2, 0 0.4 1.8 0.4 6.4 1, 0 4.4 1.0

Mating 0 0 0 0 0 0 0 0 0 0 0 0

Aggression 0 0 1.8 0.3 2.0 0.5 3.7 0.8 1.4 0.3 1.6 0.4

Diversionary 0 0 0 0 0 0 0 0 0 0 0 0

Nest Building 0 0 0 0 0 0 0 0 0 0 0 0

Incubation 0 0 0 0 0 0 0 0 0 0 0 0

Upright 2.1 1.2 1.4 0.4 8.2 1.8 1.8 0.4 9.0 1.5 4.7 1.0

Parental 0 0 0 0 0 0 0 0 0 0 0 0

Absent 0 0 0 0 0 0 0 0 0 0 0 0

Total 177; 6 496; 2 472:5 423; 2 599; 8 478; 3

APPENDIX 6. Diurnal Time Budget with Categories of BOlavior

min.

0600-0800cc

°Z, min. '76 min.

TIME PERIOD0800-1000

.mm. min

1000-1200cf min.

Stage 1Feeding 99.0 33.0 99.0 33, 1 40.7 7. 1 62.8 11.0 150.8 38.7 166.3 42. 6

Resting 63, 7 21.2 75.0 25.0 388.7 68.2 401.3 70.4 104.8 26.9 97, 5 25.0

Preening 35.3 11.8 62.5 14.2 83.7 14,7 55.0 9. 6 19.1 4. 9 25.7 6. 6

Other maint .activities

2. 0 0.8 3. 3 1, 2 3, 5 O. 6 2. 3 0, 4 1. 8 O. 5 2. 8 0. 7

Mating 11.0 3. 6 10, 8 3, A 0 0 0 0 14.5 3.7 14. 8 3., 7

Aggression 6.0 2. 0 4, 0 1,4 7. 0 1. 2 6.0 1.0 10.7 2.7 8. 3 2. 1

Diversionary 0 0 0 0 0 0 0 0 0 0 0 0

Nest Building 57.0 19.0 50, 0 16.0 35.1 6. 2 21.3 3.8 50.0 12.8 39.3 9. 2

Incubation 0. 3 0. 1 0. 3 0. 1 0 0 0 0 0 0 0 0

Upright 22.3 7. 5 13.1 4.4 9.7 1.7 20.0 3. 5 33.1 9. 0 32.3 9. 6

Parental 0 0 0 0 0 0 0 0 0 0 0 0

Absent 0 0 0 0 0 0 0 0 0 0 0 0

Total 296.6 318. 0 568, 4 568.7 384.8 392.0

Stage 2Feeding 608.5 28.4 325.8 22.6 266..5 20.2 279.1 21.2 386.0 23.6 376.5 23.2

Resting 9.5 0.7 59.5 4.1 70.8 5.2 62.0 4.7 57.5 3.5 157.7 9.7

Preening 146.5 10.2 150.0 10.4 304.8 11.7 168.5 12.8 144.8 8.9 138.0 8. 5

Other Tri a int .

activities10.7 0. 7 8,8 0, 6 7.0 0. 6 5.3 0.3 7.8 0. 5 8.8 0. 5

Mating 17.8 1. 2 17.3 1. 1 2.3 0. 1 2. 5 0. 2 S. 3 0. 2 2.8 0. 2

Aggression 14.5 0. 8 12.8 0.8 5. 7 0.3 8. 7 0. 7 4, 7 0. 2 12. 3 0. 6

Diversionary 2. / 0, 1 3.8 0. 2 8. 3 0. 6 15.3 1. 2 3. 5 0, 2 3. 1 0. 2

Nest Building 66.3 4. 6 23.3 1. 6 60.1 4. 5 39.5 3. 1 68.3 4, 3 30. 5 1. 9

Incubati on 449.7 31, 2 723.3 50.3 5 39. 8 40.9 607.0 46.0 709, 0 43, 8 702.8 43.4

Upright 42.8 3.0 35.8 2. 5 39.3 3.0 84.5 7. 7 32.7 2.0 63.7 3.9

Parental 0 0 0 0 0 0 0 0 0 0 0 0

Absent 261.8 18.2 70, 3 4.9 1 55.5 11.8 19.1 1.5 193.3 11.9 110.7 6.8

Total 1630. 2 1430.1 1460. 1 1291.5 1612.9 1606.9

APPENDIX 6. Continued

min,1200-1400

w min, min,

TIME PERIOD1400-1600

min, min.1600-1800

min.Stage 1

Feeding 13O,7 43,h z14.7 4r,8 163, 0 45,S 180. 3 50.1 194,3 53. 9 206.s 57,4Resting 11u,7 39. 6 t3,8 26. 6 1 02. 3 28. 4 108. 1 30. 1 74,8 2O,8 52. 5 t4.6Preening s,0 1.J 9,8 3.B f8,7 1O,7 40,S 11,u 43,O 11.9 38,S 1O,7Other maint.

activities0,3 g,3 1,O 0,4 10. 5 2,8 S,8 1,s 0,s 1^8 9,0 3,4

Mating 6. 0 2. 0 9.1 3^9 5,O 1,3 S,3 1.4 4,0 1,J 3. 5 0,9Aggression *.3 1.3 4,0 1,7 9,O u,0 4,7 1,% 11,7 3.0 11,8 3.4Diversionary 0. 5 0, 2 0 0 0 0 0 0 3,O 0,Q u.8 O,7Nest Building S0,7 1Q,3 28, 1 H,& 13,O 3,7 7,S u,1 9,7 2,h 7.0 1,9Incubation 0 0 0 0 0 0 0 0 0 0 0 0Upright h,8 u,3 9,8 «,1 10.3 2,9 h,1 1,7 10,3 3.0 2.8 7,eParental 0 0 0 0 0 0 0 0 0 0 0 0Absent 0 0 0 0 h.8 1,9 0 0 1.3 0.4 0 0

Total 300,0 239,s 3S8.6 358,1 358. 8 334,4

Stage 2Feeding 383. 5 36. 5 326. 0 31,0 3 00. 1 23. 3 342. 8 26. 6 603, 5 22. 6 1s8,7 17. 6Resting 7,7 0,Y 9.0 0.9 h5.7 s.1 @6.1 s.1 34,0 6.O 33,S 6,7Preening 95. 1 'J. 1 t8,9 6. 5 1 14. 0 8,8 164. 8 12,8 1o8,7 12.1 62. 5 0.9Other maint.

activities4.8 O.3 J,7 8,S 13'1 1.4 z2.0 1.8 5.0 0,S 8,s LO

Mating 0 0 0 0 1,7 0, 1 0,S 0 0, 1 0 0. 1 0Aggression 3,1 0,s 11^3 1.0 h,1 0,s h,3 0,S 9,1 1,0 h.7 0,7Diversiongry 7.3 Q,0 4.8 0,3 u,8 0. 2 2. 3 0,u 1.1 0,1 o,1 0,zNest Building 41,/ 3,9 32, 7 3,1 25, 0 1,9 10,S O,9 9. 0 1,0 7,s 0,pIncubation 390,1 37,2 516. 3 49,u h17,7 47.9 495.1 38.4 30h,8 34,1 43S^1 4B,1Upright 28. 7 m,7 u1.3 u.1 S5.7 u.7 23. 3 1.8 u0,1 2, 2 30,3 3,SParental 0 0 0 0 0 0 0 0 0 0 0 0Absent 80,a 7.7 51. ; 4.9 94,S 7,3 14s,0 11,2 146,0 11, 2 152. 1 1h,9

Total 1043, 7 1044, 8 11 62. 2 1278, 7 1293. 2 894. 9

APPENDIX 6. Continued

min,

0600-0800

% min. min.

TIME PERIOD0800-1 000

% min. % min.

1000-1200

% min, %

Stage 3Feeding 97.5 40.6 74.1 30.9 0 0 0 0 49.5 23.6 77.1 36.7Resting 18.0 7.5 0 0 2.7 8.9 0 0 35.5 16.9 35.8 17.1Preening 22.3 9.3 39.3 16.4 6.5 21.7 3.1 10.6 12.8 6.1 7.0 3.3Other maint.

activities0.1 0.1 0.1 0.1 0.1 0.6 0 0 0.7 0.3 0.1 0./

Mating 0 0 0 0 0 0 0 0 0.1 0.1 0 0Aggression 5.3 2.2 3.5 1.4 0.5 1.7 1.0 3.4 3.8 1.9 2.7 1.4Diversionary 1.5 0.6 0.7 0.3 0 0 0.3 1.1 2.5 1.2 12.7 6.1Nest Building 0.1 0.1 0 0 0 0 0 0 0.8 0.4 0.1 0.1Incubation 0 0 0 0 0 0 0 0 0 0 29.8 14.2Upright 51.7 21.5 94.8 39.5 11.5 38.4 3.5 11.7 81.8 39.0 37.0 17.6Parental 37.7 15.7 7.7 3.2 3.5 8.3 0 0 19.5 9.3 5.0 2.4Absent 0 0 13.8 5.8 6.0 20.0 21.3 71.1 0 0 0 0

Total 234.2 234.0 30.8 29.2 207.0 207.3

Stage 2Feeding 68.7 76.3 68.1 75.7 11.1 67.2 95.7 31.9 57.0 23.8 62.0 25.8Resting 17.3 19.3 18.5 20.6 95.0 31.7 128.1 42.7 151.1 63.0 128.8 53.7Preening 1.3 1.5 0.1 .2 87.1 29.1 71.1 23.7 22.7 9.4 38.7 16.1Other maint.

activities0.7 0.8 0.8 0.9 2.8 1.0 2.1 0.7 0.7 0.3 1.3 0.5

Mating 0 0 0 0 0 0 0 0 0 0 0 0Aggression 0 0 0 0 0.7 0.2 1.1 0.4 1.0 0.5 1.0 0.5Diversionary 0 0 0 0 0 0 0 0 0 0 0 0Nest Building 0 0 0 0 0 0 0 0 0 0 0 0

Incubation 0 0 0 0 0 0 0 0 0 0 0 0Upright 0.8 1.0 L3 1.5 1.7 0.6 0.7 0.2 3.5 1.5 4.7 2.0Parental 0 0 9 0 0 0 0 0 0 0 0 0Abs ent 0 0 0 0 0 0 0 0 0 0 0 0

Total 88.8 88.8 298.4 298.8 236.0 236.5

APPENDIX 6. Continued

min.1200-14d%

00-mm. %

cfmin.

TIME PERIOD1400-1600% min. % min.

1600-1800min.

Stage 3Feeding 52.8 35.2 40.7 27.1 19.5 32.5 21.7 36.1 170.8 33.5 140.1 27.5

Resting 0.5 0.3 14.5 917 2.5 4.2 2.1 3.6 44.0 8.6 73.7 14.4

Preening 3.7 2.4 4.7 3.1 4.1 6.9 8.1 13.6 43.7 8.6 51.3 10.1

Other maint.activities

1. 3 0.9 0. 5 0. 3 0. 1 0. 3 0 0 3. 1 0. 7 1. 7 0. 3

Mating 0 0 0 0 0 0 0 0 0 0 0 0

Aggression 7.0 4.6 3.8 2.5 2.7 4.5 0.1 0.3 19.5 3.9 8.7 1.6

Diversionary 2. 3 1.5 2.5 1.7 0. 1 0. 3 0 0 6.8 1. 3 2. 3 0.5

Nest Building 0 0 0 0 0 0 0 0 0 0 0 0

Incubation 0 0 0 0 0 0 0 0 0 0 0 0

Upright 72.7 48.4 61.7 41, 1 29.8 49.7 22.7 37.8 148.0 29.0 147.3 28.9

Parental 7.8 5.2 20.8 13.9 0.3 0.6 1.5 2.5 47.7 9.3 50.7 9.9

Absent 0 0 0 0 0 0 3.1 5.3 6.7 1.3 16.5 3.2

Total 148.1 149.2 59.1 59.3 490.3 492.3

Stage 4Feeding 149.1 71.0 1 33. 7 63.7 200.7 66.9 172.7 57.6 116.5 48.5 89.8 37.4

Resting 21.0 10.0 34.1 16.3 56.8 18.9 61.5 20. 5 64. 0 26. 7 54.0 22. 5

Preening 39.5 17.2 38.5 18.3 36.3 12. 1 55.0 18. 3 52. 5 21.9 90.8 37.8

Other maint.activities

1.0 0. 5 0.8 0.4 2.7 0.9 3. 7 1. 2 2. 3 1. 1 2. 1 0.9

Mating 0 0 0 0 0 0 0 0 0 0 0 0

Aggression 2.0 0.9 1.7 0.8 1.3 0.5 0.1 0.1 0.8 0.3 0.8 0.4

Diversionary 0 0 0 0 0 0 0 0 0 0 0 0

Nest Building 0 0 0 0 0 0 0 0 0 0 0 0

Incubation 0 0 0 0 0 0 0 0 0 0 0 0

Upright 0.8 0.3 1.0 0.5 2.0 0.7 7.0 2.3 3.0 1.3 1.7 0.7

Parental 0 0 0 0 0 0 0 0 0 0 0 0

Absent 0 0 0 0 0 0 0 0 0 0 0 0

Total 213.4 209.8 299.8 300.0 239.1 239. 2

1 43

APPENDIX 7

Calculation of Standard Metabolism

There is an approximately inverse linear relationship between standard

metabolism and temperature in birds (King and Farner, 1961). This

relationship is weight dependent. Standard equations have been

calculated to represent these relationships for non-passerine birds

at different temperatures (Kendeigh, 1970):

At 30 ° C, log M = -0. 26 73 + 0. 7545 log W t 0.063

At 0 ° C, log M = O. 63 72 + 0. 5300 log W t 0. 0613

where

M = Standard metabolism as Kcal/bird/day

W = Weight in grams

= Standard error of the estimate of log M

for avocets, W(average) = 316 g (Hamilton, 1969)

Therefor e;

at 30 ° C, M = 33.3 ± 0.063

at 0 ° C, M = 91. 7 ± 0.0613

Assuming a linear relationship between standard metabolism and

temperature, the standard curve of this relationship for avocets is

approximately:

0 10 20

Temperature (C°)

30

144

From this graph the increase in standard metabolism due to changes

in ambient temperature can be estimated.