27

Notes

Why Do Male Belted KingfishersWinter Farther North Than Females?

byRon Pittaway

Belted Kingfishers ICeryle alcyon) arecold-hardy and often winter as farnorth as open water permits IBent1940). During the last four winters11991-1994), I recorded the sex of thekingfishers observed wintering insouthern Ontario. Observations weremade at Bobcaygeon, Lakefield,Minden, Toronto and Whitby - allsituated north of Lake Ontario. Givena good view, it is quite easy todistinguish males from females in thefield IGodfrey 1986). Interestingly, allthe kingfishers In = 12) seen wellenough to classify were males. InYellowstone National Park,Wyoming, Skinner lin Bent 1940) alsonoted that all of the kingfisherswintering along streams kept open byhot springs were males. The firstfemales arrived there on 17 March.

Why do male kingfishers winterfarther north than females? Myhypothesis is that the number of nestsites in the northern part of theBelted Kingfisher's range is the majorfactor limiting their populations.Kingfishers usually dig their nestingtunnels in stream banks and oldgravel pits, often some distance fromwater IGodfrey 1986). Males arrivefirst on the breeding grounds anddefend a nest site. "When the female

arrives, she seems attracted to thenest site and then pairs with themale. The two then defend the nestsite and fishing area" IStokes andStokes 1983). Godfrey 11986) statesthat breeding populations in rockyareas le.g. Canadian Shield) arelimited by the availability of nestingsites. Therefore, male kingfishers thatdefend winter territories on or nearthe breeding grounds would have thefirst choice of the best breedinghabitats Inest sites and fishing areas).Returning females are apparentlymost attracted to those males holdingthe best breeding territories.

Of course, there may be otherequally valid explanations why onlymale kingfishers are found at thevery northern part of their winterrange. I would be interested inhearing about any winter IDecember­February) sightings of femalekingfishers in southern Ontario andabout other hypotheses.

AcknowledgementsI thank Bill Crins, Michel Gosselin,Jean Iron, Ron Tozer and MikeTurner for much valuable assistanceand advice in the preparation of thisnote.

VOLUME 12 NUMBER 1

28

Literature citedBent, A.C. 1940. Life Histories of North

American Cuckoos, Goatsuckers,Hwnmingbirds and Their Allies. Part 1.United States National Museum Bulletin 176,Washington, D.C.

Godfrey, W.E. 1986. The Birds of Canada.Second Edition. National Museum ofCanada, Ottawa.

Stokes, D. W. and L.Q. Stokes.. 1983. A Guide toBird Behaviour. Volume II. Little, Brown andCompany, Boston and Toronto.

Ron Pittaway, Box 619, Minden, Ontario KOM 2KO.

Grasshoppers as Food Sourcefor Black-billed Cuckoo

byDavid Agro

The most frequently noted food itemsof the Black-billed Cuckoo (CoccyzuserythropthalmusJ are caterpillars,particularly the "hairy" species (Bent1940, Godfrey 1966, Terres 1980J.Other animals such as grasshoppers,beetles, crickets, mollusks, and fishesare mentioned as prey, but little hasbeen noted on their importance aspart of the cuckoo's overall diet. Myexamination of gizzards andproventriculae of two Black-billedCuckoos found short -hornedgrasshoppers (Order Orthoptera:Family AcrididaeJ to be the majorfood item.

Both birds were road kills. Thefirst bird was an adult female, foundbarely alive near Nanticoke, R.M.Haldimand-Norfolk, in the lateafternoon on 24 July 1993. Thesecond bird, an adult male, wasfound recently killed in the earlymorning near the intersection ofHighway 24 and Regional Road 10(Turkey Point RoadJ R.M.

ONTARIO BIRDS APRIL 1994

Haldimand-Norfolk, on 1 August1993. The first bird, presumablyfeeding for most of the day, had eightwhole grasshoppers and a number ofparts that were identified as agrasshopper. There was only one partthat could be determined as beingfrom another insect, identified as acaterpillar (LepidopteraJ. The secondbird had two whole grasshoppers andnumerous grasshopper parts, plus asmall amount of caterpillar hair. Ithad proportionately less food in itsproventriculus and gizzard than thefirst, possibly due to less feedingtime.

The number of grasshoppers inthese birds suggest that cuckoos donot always depend mainly oncaterpillars for the large portion oftheir diet. At times when caterpillarsare not plentiful, the birdspresumably take advantage of other,more abundant food sources such asgrasshoppers.

AcknowledgementsI would like to thank M.E. Gartshore,R.W. Knapton and J.D. McCrackenwho made helpful comments on themanuscript, and the Long Point BirdObservatory for its support.

29

Literature citedBent, A. C. 1940. Life Histories of North

American Cuckoos, Goatsuckers, Humming­birds, and Their Allies. Part 1. UnitedStates National Museum Bulletin 176.Washington, D.C.

Godfrey, W. E. 1966. The Birds of Canada.National Museum of Canada Bulletin 203.Ottawa.

Terres, J. K. 1980. The Audubon SocietyEncyclopedia of North American Birds.National Audubon Society, New York.

David Agro, Long Point Bird Observatory,Box 160, Port Rowan, Ontario NOE 1MO.

Mourning DovesWintering in Ontario

byRon Tozer

IntroductionThe Mourning Dove (Zenaidamacroura) occurred only sparingly insettled areas of southern Ontario 150years ago (Snyder 1957), but hadbecome a common breeding speciesof the southwestern part of theprovince by early in this century(Baillie and Harrington 1936). Formany of these early years theMourning Dove was migratory inOntario (Saunders and Dale 1933).Overwintering apparently developedin agricultural areas due to theavailability of waste and stored corn(Alison 1976; Armstrong and Noakes1983). It was not until the early 1950sthat wintering populations insouthern Ontario "increased rapidlyand in a linear fashion" (Armstrong1987), apparently correlated with"corresponding increases in corn

production" (Armstrong and Noakes1981). The number of overwinteringMourning Doves in southern Ontariocontinues to increase today. Whereagricultural land has been taken overby urban development, the specieshas adapted through extensive use ofwinter bird feeders (Tozer andRichards 1974; Alison 1976). Inrecent years, the Mourning Dove hasbegun to winter even farther north incentral Ontario, away fromagricultural areas. This note examinessome of the data which illustratethese trends in wintering byMourning Doves in Ontario.

Southern OntarioFreedman and Riley (1980) trac;ed

population trends of various birdspecies wintering in southern Ontariothrough an analysis of annual

VOLUME 12 NUMBER 1

30

Christmas Bird Count (CBq datafrom seven locations (Hamilton,Kingston, Kitchener, London, Ottawa,Pickering and Toronto) during theperiod from 1929 to 1977. Theirfindings for the Mourning Doveindicated that "essentially no birdswere recorded prior to 1950",followed by relatively low (butincreasing) numbers during the nexttwo decades. Then "a spectacularincrease" occurred from 1970 to1977, with the combined totals for allseven sample counts averaging about1350 birds per year (Freedman andRiley 1980). Using the same methodon CBC results reported in AmericanBirds from the seven selectedlocations over the next fifteen years(1978 to 1992), I found an average of3479 Mourning Doves per year(ranging from 1288 in 1982, to 5226in 1988). These sample count resultswere standardized to "birds perobserver" in order to compensate forincreasing observer effort over time,as suggested by Raynor (1975).Freedman and Riley (1980) found apeak of about six birds per observerin 1976, while I calculated that therewere 10.2 Mourning Doves perobserver by 1988. The dramaticincrease in wintering by MourningDoves in southern Ontario hasobviously continued.

I examined all Ontario CBC datareported in American Birds during thetwenty years from 1973 to 1992 inorder to further investigate themagnitude and timing of the increasein Mourning Dove numbers. Insouthern Ontario (south of theCanadian Shield), there were fully 15Christmas Counts which achievedtotals of 1000 birds (or more) duringthe 1980s. The average year of thesecounts first reaching that "plateau"

ONTARIO BIRDS APRIL 1994

was 1987. Two southern OntarioCBCs have actually reached totals ofmore than 2000 Mourning Doves (Le.2016 at Cedar Creek in 1987, and2001 at St. Catharines in 1988j!

Central OntarioIn 1966, it was reported that the

Mourning Dove wintered in Ontario,"north rarely and precariously toOttawa" (Godfrey 1966). Since then,however, the species has been regular(with increasing numbers) throughoutthe twenty years from 1973 to 1992on CBCs at Ottawa-Hull, Pakenham­Arnprior, and Carleton Place. Duringthe 1980s, wintering by MourningDoves spread to various sites on theCanadian Shield. For example, theyhave become regular (with increasingnumbers) on the following CBCssince the year shown in parentheses:Pembroke (1981); North Bay, SaultSte. Marie, and Gravenhurst­Bracebridge (1982); Deep River, andMinden (1987); Sudbury (1988); andBurks Falls, and New Liskeard(1989). Mourning Doves have beenregularly observed on an unpublishedwinter bird count at Huntsville since1984 (Huntsville Nature Clubrecords).

Wintering by Mourning Doves atthese Shield communities isapparently linked to increases in localbreeding populations (Alison ::.976),and the provision of food at winterfeeding stations adjacent to denseconiferous cover for roosting. Dow(1994) has suggested a similardependency on feeders as "a factorcritical to maintaining localpopulations as breeding entities" inoutlying areas of the NorthernCardinal's (Cardinalis cardinalis) rangein Ontario. Many Mourning Dovesattempting to winter on the Canadian

Shield are totally dependent onfeeding stations, with no access toagricultural land for corn or weedseeds.

Northern OntarioVery recently, a few Mourning

Doves have been detected on CBCseven farther north. These counts,with the number of birds inparentheses, were as follows:Timmins in 1992 (6); Thunder Bay in1987(21, 1991 (11, and 1992 (11;Dryden in 1992 (11; and evenMoosonee in 1992 (31. Indicative ofthis species' continued advancenorthward in Ontario was thepresence of at least 12 birds atMoosonee during the 1991 breedingseason, with "courting and copulatingpairs" observed and breedingstrongly suspected (Wilson andMcRae 19931. The Clay Belt wasconsidered to be the northernboundary of breeding through thelate 1980s (Peck and James 1983;James 19911.

Wintering CapabilityEven with available food and

cover, severely cold winter weatheroften causes injury, and sometimeseven mortality, among MourningDoves attempting to winter innorthern areas such as Ontario(Nickell 1964; Alison 1976; Whelan19941. Frost damage to the feet,including loss of toes, is a commoninjury (Alison 197.6; Armstrong andNoakes 19831. However, birdssustaining such injuries canapparently still function. Studies ofcaptive birds (Ivacic and Labisky19731 have actually suggested thatMourning Doves may ,'possess aphysiological mechanism that allowsthem to substantially reduce their

31

body temperature and,correspondingly, their metabolicexpenditures" when exposed to lowambient temperatues and absence offood (as during winter stormsl.

Successful overwintering byMourning Doves in Ontario allowsthem to "avoid the hazard ofmigration and hunting" and to "takeadvantage of favourable early springconditions that may increase thelength of the breeding season"(Armstrong and Noakes 19831.

AcknowledgementsDiscussions with Doug Tozer andRon Pittaway were very helpful inthe preparation of this note.

Literature citedAlison, R.M. 1976. Mourning Doves wintering

in Ontario. Canadian Field-Naturalist 90:174-176.

Armstrong, E.R. 1987. Mourning Dove.pp. 196-197 in M.D. Cadman, P.F.J. Eagles,and F.M. Helleiner (Compilers). Atlas of theBreeding Birds of Ontario. University ofWaterloo Press, Waterloo, Ontario.

Armstrong, E.R. and D.L.G. Noakes. 1981.Food habits of Mourning Doves in southernOntario. Journal of Wildlife Management 45:222-227.

Armstrong, E.R. and D.L.G. Noakes, 1983.Wintering biology of Mourning Doves,Zenaida macroura, in Ontario. CanadianField-Naturalist 97: 434-438.

Baillie, ].L. and P. Harrington. 1936. Thedistribution of breeding birds in Ontario.Transactions of the Royal Canadian Institute21: 1-50.

Dow, D.D. 1994. The Northern Cardinal inSouthern Ontario. pp. 291-297 in M.K.McNicholl and J.L. Cranmer-Byng (Editors).Ornithology in Ontario. Special PublicationNo.1, Ontario Field Ornithologists.Hawk Owl Publishing, Whitby, Ontario.

Freedman, B. and].L. Riley. 1980. Populationtrends of various species of birds winteringin southern Ontario. Ontario Field Biologist34: 49-79.

VOLUME 12 NUMBER 1

32

Godfrey, W.E. 1966. The Birds of Canada.National Museum of Canada Bulletin 203.

[vacic, D.L. and R.P. Labisky. 1973. Metabolicresponses of Mourning Doves to short-termfood and temperature stresses in winter.Wilson Bulletin 85: 182-196.

James,. R.D. 1991. Annotated Checklist of theBirds of Ontario. Second Edition. LifeSciences Miscellaneous Publications. RoyalOntario Museum, Toronto.

Nickell, W.P. 1964. The effects of probablefrostbite on the feet of Mourning Doveswintering in southern Michigan. WilsonBulletin 76: 94-96.

Peck, G.K. and R.D. James. 1983. BreedingBirds of Ontario: Nidiology and Distribution.Volume 1: Nonpasserines. Life SciencesMiscellaneous Publication. Royal OntarioMuseum, Toronto.

Raynor, G.S. 1975. Techniques for evaluatingand analyzing Christmas Bird Count data.American Birds 29: 626-633.

Saunders, W.E. and E.M.S. Dale. 1933. Historyand list of the birds of Middlesex County,Ontario. Transactions of the Royal CanadianInstitute 19: 161-248.

Snyder, L.L. 1957. Changes in the avifauna ofOntario. Pp. 26-42 in F.A. Urquhart (Editorl.Changes in the Fauna of Ontario. Universityof Toronto Press, Toronto.

Tozer, R.G. and].M. Richards. 1974. Birds ofthe Oshawa-Lake Scugog Region, Ontario.Published by the authors.

Whelan, P. 1994. Mourning Doves cling to life.Globe and Mail (15 January 1994).

Wilson, N.C. and D. McRae. 1993. Seasonaland Geographical Distribution of Birdsfor Selected Sites in Ontario's Hudson BayLowland. Ontario Ministry of NaturalRe~urces. Moosonee.

Ron Tozer, R.R. I, Dwight, Ontario POA IHO.

Successful Hybridization ofCommon Raven and American Crow

byE.A. (Beth) Jefferson

Since 1985, a single Common Raven(Corvus corax) has frequented anurban environment approximately145 kIn south of its usual range. Ithas been observed pursuing, killingand feeding on Rock Doves (Columbalivia) and Gray Squirrels (Sciuruscarolinensis) in Metropolitan Toronto,Ontario (43 0 36'N, 79 0 31'W). Thisraven has been seen most frequentlyin the area of the former EtobicokeLakeshore Psychiatric Hospital. Twonests were built by this bird underthe eaves of one of the four-storeybuildings during the spring of 1987.

ONTARIO BIRDS APRIL 1994

At that time there was no sign of amate (Jefferson 1989).

Many observations during 1990indicated that the raven had pairedwith an American Crow (c.brachyrhynchos). During April 1990the r<lven was observed (M. Delorey,pers. corom.) performing courtshipflights around a crow. On 8 May1990, the raven was observedshredding white material, and addingit to one of the aforementioned nests.It was then seen sitting on the nestfor at least 45 minutes, with only itstail visible. The next day it was

observed flying into a Norway Spruce(Picea abies) to alight beside a crow.The raven fed the crow whatappeared to be fresh "meat", andthen mounted the crow. The ravenand crow were subsequentlyobserved allopreening (D.McClement, pers. comm.; Bent 1946).Since 1990, the raven and crow havebeen seen flying together frequently(Jefferson 1991).

In 1990, the raven began tomimic the calls of a crow, whichmight have led to its acceptance bythe crow. Vocal interactions betweenthe crow and raven have been heard- a pattern of two caws coming fromthe crow answered by three deepercaws from the raven.

In late April 1993, the CommonRaven was observed activelyconstructing a nest in a crotch of aspruce tree on the above site. Thenest was approximately 60 em indiameter and 40 em deep, one metrefrom the top of a nine to ten metrehigh tree. During the next twomonths the raven was occasionallyseen on the nest; invariably it wasobserved perched nearby, well­concealed in the spruce branches. Ina few instances, when intruders camerather close to the nest, it flew fromelsewhere on the property intoneighboring trees.

A crow was thrice seen leavingthe nest, but all nests were too deepfor any observations of a crow sittingthere. On 29 May 1993, the crow wasviewed leaving the nest area toconfront a high-flying Turkey Vulture(Cathartes aura). Three minutes later,as the crow dropped back down, theraven flew up to meet it; both corvidsthen returned to the nest site (G.Fairfield, pers. comm.).

33

On several occasions - 3, 5 and 8May 1993 - after consuming severalpieces of squirrel, the raven flew tothe nest where it remained for 40-60seconds. Precise activity at the nestwas obscured by the dense evergreenbranches.

On 14 June begging calls wereheard from the nest vicinity (A.Fairbridge, pers. comm.). The nextday the author observed muchactivity around the nest, with a crowand raven repeatedly calling to eachother. What were later deemed to betwo recently fledged hybrids madeshort flights between nearbydeciduous trees. On 18 June 1993positive confirmation was made ofthe two hybrids. They were almostraven-sized, with the wedged-shapedtail of a raven and the head of acrow. Their bills appeared very thin,shorter than that of a crow, with asmall amount of yellow at the gape.The two hybrids were photographedseveral hundred meters south of thenest in the crowns of large mapletrees (see Figure I).

Repeatedly, both the crow andraven flew away from the youngbirds making loud distracting noiseswhenever these fledglings wereapproached; a few minutes later theadults would silently appear frombehind the observers. This behaviourwas noted frequently over a 90minute period. Begging calls from theyoung were silenced when the crowflew into the trees where the youngremained. Dense foliage preventedprecise observations of behaviourfrom our position 10 m to the north.Later, cawing from these fledglingssounded more highly pitchedcompared to that of the crow, whichin turn made calls which were higher

VOLUME 12 NUMBER 1

34

Figure 1: Recent fledgling resulting from the hybridization of Common Ravenand American Crow at the former Etobicoke Lakeshore PsychiatricHospital, Metropolitan Toronto, Ontario, Canada, 18 June 1993.Photo by Beth Jefferson.

than the deep resonating caws fromthe raven. The crow, raven and twohybrids continued to be seen flyingtogether until the end of June (D.McClement, pers. comm.). Duringthe fall of 1993, the two hybrids wenfrequently observed with the raven.On 27 October, all of them were seenbriefly by the author chasing 'RockDoves.

Both sexes of crow take an activepart in nest building. Both sexes ofravens also contribute to the buildingof a nest and both sexes of crow mayhelp incubate (Bent 1946: Goodwin1976). With ravens, the male is notreported to incubate but only to coverthe eggs when the female leaves thenest. In corvids the male feeds thefemale during incubation and thefemale sometimes leaves the nest tobe fed by the male nearby (Bent1946: Goodwin 1976). From these

ONTARIO BIRDS APRIL 1994

descriptions and the other directobservations cited above, it has beenconcluded that the raven is a maleand that the crow is a female.

If fledging took place 14 June1993, the eggs would have hatched inearly May during which time theraven was observed making frequenttrips to the nest after ingestingsquirrel meat. If the crow laid theeggs as is speculated, it would haveoccurred approximately 18 days priorto this in the second week of April.These dates have been deduced usingaverages cited in Ehrlich et al. (1988).

This appears to be the firstknown documentation of successfulhybridization of Common Raven XAmerican Crow in North America. InBritain, three reports of hybridizationof Common Raven X Carrion Crow(c. carone) are cited in Gray (1958).

But these records date from 1897 to1936. If undocumented raven X crowhybridization has occurred, it wouldbe virtually impossible to distinguishin any of their offspring. (Forexample, visual hybrid featureswould not be as apparent as inLawrence's and Brewster's Warblers.)The atypical location of thisparticular raven, and thedistinguishing silvery-gray cast to itsback and wings creating a two-tonedeffect in flight, have enabled thisparticular raven to be subjected tointense scrutiny. Thus details of itsbehaviour have been noted by manybirdwatchers.

Prior to the spring 1993observations described above, in May1992 (G. Coady, pers. comm.) andduring the winter of 1992-1993,"small ravens" were seen in thevicinity of the hospital. In addition,on 13 November 1993, a small raven­shaped bird was observed beingchased by two crows, several kmnorthwest of the hospital grounds,above High Park. This corvid wasonly slightly larger than the pursuingcrows (B. Yukich, pers. comm.). It isspeculated that these smaller"ravens" might possibly be hybridsfrom previous years. The 1993 adulthybrid "cravens", as they have beenunofficially dubbed, closely resemble

35

a raven. Identification could be quitetricky, especially if they leave theirnatal area.

AcknowledgementsI appreciate the continuedencouragements from AlvaroJaramillo and Jim Rising, ZoologyDept., University of Toronto, andfrom Don McClement, who havecommented on earlier drafts of thisnote and have offered many insightsrespecting hybridization possibilities.

Literature citedBent, A. C. 1946. Life Histories of NorthAmerican

Jays, Crows and Titmice. United StatesNational Museum Bulletin 191, Washington,D.C.

Ehrlich, P.R., D.S. Dobkin, and D. Wheye.1988. The Birder's Handbook. A Field Guideto the Natural History of North AmericanBirds. Simon & Schuster. New York, N.Y.

Goodwin, D. 1976. Crows of the World. CornellUniversity Press, Ithaca, New York.

Gray, A.P. 1958. Bird Hybrids - A Checklistwith Bibliography. CommonwealthAgricultural Bureaux. Farnham Royal,Bucks, England.

Jefferson, B. 1989. Observations of CommonRaven in Metropolitan Toronto. OntarioBirds 7: 15-20.

Jefferson, B. 1991. Evidence of pair bondingbetween Common Raven (Corvus corax) andAmerican Crow ICorvus brachyrhynchosl.Ontario Birds 9: 45-58.

E.A. (Beth) Jefferson, 41 Lake Shore Drive, Apt. 404,Etobicoke, Ontario M8V 1Z3

Red-Shouldered Hawk SurveyIn 1994 and 1995, volunteers are needed toplay taped recordings of this rare raptor'scalls, and note the number and age of thoseindividuals which respond along selectedsurvey routes in south-central Ontarioduring late April. Routes consist of 20stations over 19 km, and take about four

hours to complete (starting just after sun­rise). Surveyors are given a tax receipt formileage and out-of-pocket expenses.Contact: Lisa Enright, Long Point BirdObservatory, Box 160, Port Rowan, OntarioNOE 1MO. Telephone (5191 586-3531.

VOLUME 12 NUMBER 1