Study Unit Wildlife Management: Waterfowllessons.pennfoster.com/pdf/022006.pdf · 2017-11-30 · The necks of most waterfowl are long. This allows them to reach down through the water

Study Unit

Wildlife Management:WaterfowlBy

David Caithamer, Ph.D.

All terms mentioned in this text that are known to be trademarks or serv-ice marks have been appropriately capitalized. Use of a term in this textshould not be regarded as affecting the validity of any trademark or serv-ice mark.

About the Author

David Caithamer was born and raised in the suburbs of Chicago. He holds a Bachelor of Science degree in Wildlife Management fromthe University of Wisconsin, Stevens Point; a Master of Sciencedegree in Biology from Tennessee Technological University; and aDoctor of Philosophy degree in Zoology from Southern IllinoisUniversity. His doctoral research involved the behavior and energet-ics of Canada geese. During his college years, he taughtundergraduate laboratory classes in various biology courses.

Dr. Caithamer also worked on waterfowl areas for the WisconsinDepartment of Natural Resources and the U.S. Fish and WildlifeService during summer breaks. After completing his doctorate, he worked as a waterfowl biologist for two years with the IndianaDepartment of Natural Resources. He then worked for seven years with the Office of Migratory Bird Management, U.S. Fish and Wildlife Service. While with the Office of Migratory BirdManagement, he assessed the status of various waterfowl popula-tions and helped develop waterfowl hunting regulations. Presently,Dr. Caithamer works as a biology consultant. He also owns andmanages a resort in northern Wisconsin.

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This unit will introduce importantaspects of the biology and managementof waterfowl in North America. Emphasisis placed on the most common NorthAmerican species. However, you’ll alsolearn biologic concepts that apply to many other species. This study unit

will describe the life cycles and habitat requirements of representative species, explain the surveys and data thatwildlife managers use, and outline the annual process ofestablishing waterfowl hunting regulations. You’ll also learnpractical techniques, such as how to capture waterfowl andimprove nesting success.

When you complete this study unit, you’ll be ableto • Recognize features unique to waterfowl

• Identify several of the common species of waterfowl

• Contrast the life cycles of the mallard duck and theCanada goose

• Provide examples of factors that may limit waterfowl populations

• Describe the process used to establish mallard hunt-ing regulations in the United States

• Compare methods used to estimate size, harvest,and movements of waterfowl populations

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WHAT ARE WATERFOWL? 1

Anatomic Features and Adaptations 1Taxonomy 3

IDENTIFICATION AND NATURAL HISTORY 10

Dabbling Ducks 10Perching Ducks 15Bay Ducks 18Mergansers and Sea Ducks 21Stiff-Tailed Ducks 23Geese 24Swans 27

BASIC BIOLOGY 32

Reproduction 32Nutrition 33Molting and Plumage 35Migration 38Field Characteristics of Age and Sex 40Population Dynamics 41

MANAGEMENT OF HABITAT 49

Limiting Factors 49Habitat Management Techniques 50Who Manages a Habitat? 55

MANAGEMENT OF POPULATIONS THROUGHHARVEST 59

The Science of Population Management 59Administration of Hunting Seasons 61

MONITORING WATERFOWL POPULATIONS 65

Population Size 65Harvest 69Tracking Waterfowl 70

SELF-CHECK ANSWERS 77

EXAMINATION 81

Contents

Contents

1

WHAT ARE WATERFOWL?Waterfowl are an extremely successful, adaptable, and wide-spread group of birds. They’ve evolved over the last 50 millionyears to live partly on land and partly on water. They neston all continents of the earth, except Antarctica. In NorthAmerica, the size of the waterfowl population exceeds 100million ducks, geese, and swans. Many species of waterfowlhave been used for food since prehistoric times. They’re stillpopular game birds with contemporary hunters.

Because of their beautiful coloration, conspicuous migrations,and interesting behavior, waterfowl have been popular withbird watchers for decades. Fortunately, most waterfowl havebeen extensively studied. There’s a large body of scientificknowledge about them. In this unit, you’ll learn about someof the most important aspects of their life history and biology. You’ll also learn techniques used by waterfowlmanagers and researchers.

Anatomic Features and AdaptationsProbably you’re already familiar with several different typesof waterfowl. Like other birds, waterfowl have feathers and afour-chambered heart, and they can regulate their bodytemperature. What you may not know is what sets waterfowlapart from other birds.

Consider the mallard, a common type of waterfowl acrossNorth America that’s familiar to many people. The mallard,like other waterfowl, exhibits certain anatomic features that

Wildlife Management: Waterfowl

make it well adapted for a semi-aquatic existence. All water-fowl have webbing between their front three toes. Webbingenhances their efficiency when swimming.

The beak on waterfowl is usually flattened and rounded atthe end and is called a bill. The inner edges of the bill arefringed with strainer-like structures called lamellae that aidin filtering small food items from the fine sediments ofmarshes. The tongues of waterfowl have serrated edges thataid in grasping and handling of food. The necks of mostwaterfowl are long. This allows them to reach down throughthe water to feed.

Because they spend so much time in the water, waterfowlhave well-developed oil glands and two layers of feathers.These layers work together to help keep the birds dry andwarm. The outer feathers are the rigid contour feathers, andthe inner ones are the fluffy down feathers.

The oil gland resembles a nipple and is located at the base of the tail. This gland produces a waxy or oily secretion thatthe bird spreads on all its contour feathers while preening.During this process, the bill is rubbed on the oil gland, leav-ing oil on the surface of the bill. The bill is then rubbed onthe contour feathers, spreading oil throughout the feathers.The oil keeps the contour feathers waterproof, thus ensuringthat the down feathers remain dry.

Eggs of all waterfowl are white or pale without any spots. Theeggs aren’t incubated until the last egg in the clutch is laid.The young that emerge are precocial. This means that they’realready covered with downy feathers; their eyes are open;and within about 24 hours of hatching they’re sufficientlycoordinated to walk, swim, and feed. This is different frommany other birds, like robins, for whom hatchlings have nofeathers, closed eyes, and are incapable of walking.

One final feature of waterfowl is an annual flightless period.Each year—usually in the summer months—adult waterfowlcan’t fly for about three weeks. During this time they molt orshed their wing feathers in order to grow new ones. Thismolting usually coincides with the period when the youngwaterfowl gain their ability to fly.

Wildlife Management: Waterfowl2

TaxonomyTaxonomy is the study of classifying organisms based on theirsimilarities and differences. The classification of waterfowl—like that of all other organisms—is constantly changing asnew information is revealed. The basic unit of classificationis the species. A species is a group of individuals that have asimilar appearance and are capable of interbreeding.

Each species has both a common name and scientific name.The scientific name for the mallard is Anas platyrhynchos.Scientific names often seem confusing because they’re Latinwords. The scientific name has two parts. The first part isthe genus, and the second part is the specific species name.Together, they compose a complete scientific name thatusually has a special meaning. In the case of the mallard,“Anas” means duck, and “platyrhynchos” means flat-beaked.

Species that are very similar use the same genus in theirscientific name. Therefore, they belong to the same genus. Forexample, the black duck’s genus is the same as the mallard’s(Anas). Similar genera (plural of genus) are further groupedinto tribes, similar tribes into subfamilies, and similarsubfamilies into families. This system is multilayered (Table 1)and therefore somewhat complicated. Nevertheless, for yearsthe system has been useful for scientists who work in allfields of biology.

All waterfowl belong to the family Anatidae (Figure 1). OneNorth American species—the Labrador duck—is now extinct.The Anatidae family is typically divided into 3 subfamilies and13 tribes. Worldwide there are approximately 145 species ofwaterfowl. In North America, 47 species—representing 7tribes—breed in the wild (Table 1).

Let’s look at some of the distinguishing features of the seventribes in North America.

Wildlife Management: Waterfowl 3


Table 1Classification of North American Waterfowl that Commonly Breed in the Wild

Tribe Common Name Scientific Name (Genus)Dendrocygnini Fulvous whistling duck Dendrocygna bicolor(Whistling ducks) Black-bellied whistling duck Dendrocygna autumnalis

Anserini Mute swan Cygnus olor(Swans and true geese) Trumpeter swan Cygnus buccinator Tundra swan Cygnus columbianus White-fronted goose Anser albifrons Snow goose Chen caerulescens Ross’s goose Chen rossii Emperor goose Anser canagicus Canada goose Branta canadensis Barnacle goose Branta leucopsis Brant goose Branta bernicla

Cairini (Perching ducks) Wood duck Aix sponsa Muscovy Cairina moschata

Anatini (Dabbling, puddle, or American wigeon Anas americanasurface-feeding) Gadwall Anas strepera Green-winged teal Anas crecca Mallard Anas platyrhynchos Mottled duck Anas fulvigula Black duck Anas rubripes Northern pintail Anas acuta White-cheeked pintail Anas bahemensis Blue-winged teal Anas discors Cinnamon teal Anas cyanoptera Northern shoveler Anas clypeata

Aythyini Canvasback Aythya valisineria(Bay ducks) Redhead Aythya americana Ring-necked duck Aythya collaris Greater scaup Aythya marila Lesser scaup Aythya affinis

Mergini Common eider Somateria mollissima(Mergansers and sea ducks) King eider Somateria spectabilis Spectacled eider Somateria fischeri Steller’s eider Poysticta stelleri Labrador duck (extinct) Camptorhynchus labradorius Harlequin duck Histrionicus histrionicus Old-squaw Clangula hyemalis Black scoter Melanitta nigra Surf scoter Melanitta perspicillata White-winged scoter Melanitta fusca Bufflehead Bucephala albeola Barrow’s goldeneye Bucephala islandica Common goldeneye Bucephala clangula Hooded merganser Lophodytes cuccullatus Red-breasted merganser Mergus serrator Common merganser Mergus merganser

Oxyurini (Stiff-tailed ducks) Ruddy duck Oxyura jamaicensis Masked duck Oxyura dominica


Individual Tribes

Dendrocygnini. The whistling ducks (Figure 2) of the tribeDendrocygnini have a whistle-like vocalization and long legsand necks. The plumage is similar for both sexes. Both par-ents care for the young.

FIGURE 1—Waterfowl Classification Tree


Anserini. Geese and swans belong to the tribe Anserini.These are all moderate-to-large birds. The plumage lacks iridescent colors and is similar in both sexes. The scale pat-terns on the legs are reticulate, which means that the scaleslie adjacent to each other, like tiles on a floor. Geese andswans are almost exclusively herbivores—that is, they eatplant matter and little else. They form lifelong pair bonds,don’t breed until they’re two or three years old, and bothparents care for the young.

Cairini. In North America, the wood duck and muscovy arethe only representatives of the tribe of perching ducks calledCairini. Members of this tribe often perch in trees and nestin tree cavities. They have strong claws, and their legs arewell forward on their bodies. Their wings are more roundedthan in other waterfowl, and they tend to have long tails.Both sexes often have iridescent plumage. The males tend to be much larger than females.

FIGURE 2—Black-BelliedWhistling Duck (CourtesyU.S. Fish and Wildlife Service)


Anatini. Many of the popular game ducks, including themallard, are in the tribe Anatini. These are called dabbling,puddle, or surface-feeding ducks, and they’re well adaptedfor feeding in shallow marshes. Males have elaborate col-oration, and females are brown and tan.

The secondary feathers of the wing, collectively known as thespeculum, are brightly colored on both sexes. The speculumis a key feature that aids in identification of ducks. Thescales on the legs are scutellate, which means that theyoverlap each other like shingles on a roof. The hind toe hasno lobe of flesh hanging from it. Legs are positioned forwardon their bodies, making them capable walkers. They havestrong wings that allow them to spring straight into flightfrom the surface of water. Dabbling ducks usually maketheir first attempt at breeding when they’re about one yearold.

Aythyini. This tribe represents the bay ducks, which alsoincludes many popular game ducks. Generally, these birdslack bright colors. However, the coloration of females is different from males. As with dabbling ducks, females aremostly brown.

The speculum on bay ducks is generally white, black, orgray. The scales on the legs are scutellate. The legs are farback on the body, making it difficult for them to walk buteasy for them to dive and swim. Their hind toe has a lobe of flesh, almost like another web. Their wings aren’t as welldeveloped as those of the dabbling ducks, so the bay ducksnormally must flap and run across the surface of the waterto become airborne. Typically, they first breed when they’reabout one year old.

Mergini. Mergansers and sea ducks belong to this tribe.These birds are often found in large bodies of waters, suchas the Great Lakes, estuaries, and oceans. Their legs are farback on their bodies, which makes them good swimmers anddivers but only poor walkers. They have strong or serratedbills.


The sexes have different appearances. The males are usu-ally black and white, and the females are usually mostlybrown. Breeding is delayed until the birds are two years ofage or older.

Oxyurini. The last tribe represented in North America isthe stiff-tailed ducks. Their tails are long and stiff and canbe held upright out of the water. They have rather large feet set far back on their bodies. Like members of Aythyini andMergini, stiff-tailed ducks are poor walkers but good divers.Stiff-tailed ducks also have short, thick necks and smallwings.

The males look different than the females, who tend to havedull coloration. To become airborne, they must flap theirwings and run across the water.


Self-Check 1At the end of each section of Wildlife Management: Waterfowl, you’ll be asked to pause andcheck your understanding of what you have just read by completing a “Self-Check” exercise.Answering these questions will help you review what you’ve studied so far. Please completeSelf-Check 1 now.

1. Name the nine features that help distinguish waterfowl from other types of birds.

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2. Define the term precocial.

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3. How many species of waterfowl are found in North America?

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4. Identify four characteristics that biologists use to classify waterfowl into tribes.

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Check your answers with those on page 77.


IDENTIFICATION AND NATURALHISTORY

Dabbling Ducks

Mallard Ducks

Eleven species of dabbling ducks live in North America. Themallard is the most common and widespread duck in NorthAmerica. Its natural history and ecology are typical of otherducks in the tribe Anatini. Mallards weigh about two andone-half pounds when they’re fully grown, making themsome of the largest ducks.

The male mallard (Figure 3), or drake, has an iridescentgreen head, chestnut chest, gray sides, black rump, andolive-green bill. The female, or hen, is slightly smaller, mostlybrown and tan, and has an orange bill that’s often coveredwith brown patches. In both sexes the speculum is iridescentblue-violet with white edges.

FIGURE 3—Mallard Drakes


Nesting/Mating. Mallards can be found across NorthAmerica in a wide range of aquatic habitats. In the springand summer they’re very abundant in the North CentralUnited States and South Central Canada. This broad grass-land area with its numerous shallow wetlands and lakes isknown as the Prairie Pothole region (Figure 4). These rollinggrasslands with numerous temporary wetlands and smalllakes are located in western Minnesota, the Dakotas, easternMontana, southeastern Alberta, southern Saskatchewan,and southern Manitoba. This area is the center of the nest-ing range for mallards.

Some mallards, however, nest as far north as Alaska and as far south as Texas. During the winter, mallards can befound almost anywhere that wetlands remain unfrozen.However, they’re mostly concentrated in the wetlands alongthe Mississippi River—from about Missouri southward. Eachfall and spring, mallards migrate between wintering andnesting areas.

Mallards are monogamous, which means that each femalepairs with only one male for each breeding season. Withmallards there are slightly more males than females, sosome males have no mate. Pairing occurs in fall or winter,with birds selecting a new mate each year.

FIGURE 4—Aerial View of the Prairie Pothole Region during the Spring Season(Courtesy of U.S. Fish and Wildlife Service)


The pair migrates northward together in the spring to nest-ing areas. Preferred nesting areas have numerous shallowwetlands and adjacent grassy fields. Within a week or twoafter arriving at the nesting area, the female selects a nestingsite, which is almost always on the ground in grassy vegetation or under shrubs. The drake normally doesn’taccompany the hen to the nest site. However, he does waitfor her in a nearby pond. The pair seeks isolation, so thatthey may feed without disturbance from other mallards. Thepair mates on the water. The mating process occurs aboutonce per day during the egg-laying period.

On most days, hens lay one egg per day in the nest untilabout nine eggs are laid. After laying each egg, the hen cov-ers the nest bowl with vegetation and returns to the pond torejoin her mate. The hen begins to incubate the eggs afterthe last one is laid. To accomplish this, she lies on the eggs,allowing her body to warm the eggs. Once the eggs arewarmed, the embryos can begin to grow and develop. The hencontinues to incubate the eggs almost nonstop. She breaksonly once or twice a day for less than an hour to feed anddrink. During the early stages of incubation, the pair bondbreaks down and the drake joins flocks of other drakes. Afterabout 28 days of incubation, the eggs finally begin to hatch.

If a nest is completely destroyed before hatching, the hen willnormally re-nest. During re-nesting, she may have the samemate as during the first attempt, or she may find a newmate. Re-nesting can occur several times during the springor summer, but the clutch size (number of eggs in the nest)usually gets smaller with each nesting attempt.

All the eggs in a clutch hatch within a few hours of eachother. Peeping can be heard from the ducklings (youngducks) before they emerge from the eggs. The female contin-ues to sit on the eggs and ducklings during hatching and forthe first day after hatching.

By the next day, the down-covered ducklings have dried off.They follow the hen as she walks to the nearest wetland. Theducklings can swim and feed immediately, but they remainnear the hen (Figure 5). The hen will frequently brood theducklings during the next several days. Brooding is a behav-ior in which the hen covers the young with her wings andbody to help them stay warm and dry.


The ducklings gradually grow rigid feathers and becomelarger. The hen spends less time with them. When the youngare about 50 days old, they’re capable of flying and are con-sidered fledged. By this time the ducklings have flocked withother ducklings, and the hens have abandoned them.

After abandoning the young, a hen will molt its wing feathersand be unable to fly for three to four weeks. This is usuallydone on marshes near the nesting location. Hens that wereunsuccessful at nesting fly longer distances to large marshes.There they join flocks of drakes. These unsuccessful hensand drakes undergo molting together. They’re flightless forseveral weeks during July or August.

Migration. As fall approaches, and adults and young arecapable of flight, mallards begin to gather in flocks on thebigger marshes and lakes. The shortening day lengths ofautumn cause the birds to become restless. Advancing coldweather with north winds triggers the birds to begin theirmigration, usually in September or October. Migration is aperiodic movement that brings the birds to more favorableplaces.

For mallards, the fall migration brings birds southward towarmer areas where wetlands are unfrozen and the birdscan readily feed. Mallards gather in flocks of several dozen toseveral hundred birds and fly in loose “V” formations duringmigration. These migratory flights can carry the birds severalhundred miles in a day or two.

FIGURE 5—Mallard Hen with aBrood of Ducklings (CourtesyJoel Arrington/U.S. Fish andWildlife Service Photo)


The process of migration is gradual, so that it may take amallard from October to December to travel from the nestingto the wintering area. The birds spend the winter monthsfeeding, resting, and selecting mates. By about February, the increasing day lengths again cause the urge for mallardsto migrate, but this time northward. A steady wind from thesouth normally aids them as they begin their spring migra-tion. The birds continue to advance at about the same ratethat wetlands are thawing. This means that most birdsarrive at the Prairie Pothole region sometime in April.

Mallards, like many other waterfowl, eat many aquaticinsects and other invertebrates in the first several weeks oftheir life. This diet of animal matter contains much protein,which the young need to grow and develop. As they mature,the diet of mallards changes to one of mostly seeds, includingthose from wetland plants such as smartweed, millet, andpondweed. The birds also eat seeds of upland plants, includingacorns and grains.

Other Dabbling Ducks

The 10 other species of dabbling ducks share similaritieswith the mallard. However, each has features that makes itunique. Two examples demonstrate some of this variation.

With mottled ducks, both sexes look similar to a femalemallard. They migrate only a short distance, because theynest and spend winters in the southeastern United States.

The northern shoveler has a bill that’s much larger than thatof mallards and other dabbling ducks (Figure 6). Because ofthis, shovelers are efficient at capturing small invertebratesin the water. These ducks continue to feed on the inverte-brates extensively even as adults.


Perching DucksThe wood duck and muscovy are the only two representativespecies of the tribe Cairini in North America. The wood duckis common, whereas wild muscovies are found only insouthern Texas.

The wood duck has been domesticated for commercial meatproduction, but this bird is a more important naturalresource in North America. Many people believe that thewood duck (Figure 7) is the most colorful duck in NorthAmerica. The maleshave elaborate mark-ings over their entirebody. Their heads aredark green and bluewith white stripes anda distinctive crest atthe rear. The smallbill is mostly brightorange. The chest onthe male is darkbrown with whitespots, the sides aregolden, and the tail islong and dark.

FIGURE 7—Wood Duck Pair (Courtesy U.S. Fish and Wildlife Service)

FIGURE 6—Shoveler


Female wood ducks are similar to males, but with morebrown hues and less bright colors. The head of a female hasno white stripes, but rather a white ring around the eyes. Inboth sexes the speculum is iridescent blue, purple, andpink, with fine white edging. Wood ducks are medium-sizedducks and grow to about one and one-half pounds.

Wood ducks live mainly in forested swamps. They’re commonthroughout the eastern United States and the West Coast.They’re absent from the Plains states where trees are scarce.

Nesting/Mating. Wood ducks nest throughout the easternUnited States, but they’re most numerous along rivers andin coastal areas of the Southeast. The forested swamps ofthe Southeast are also important wintering areas for woodducks. Thus, many wood ducks migrate only a short dis-tance—or not at all—between their southern nesting andwintering areas.

Wood ducks are monogamous, forming pair bonds duringthe fall and winter. Pair bonds are formed with a new mateeach year. Wood ducks first attempt breeding when they’realmost one year old and normally attempt nesting every year.Nesting occurs in the spring, beginning anytime from Februaryin the south until late April near the Great Lakes. The malewood duck follows the hen to the nesting area. Females willoften return to the area where they were hatched or to thesame site where they nested previously.

Wood ducks nest in tree cavities left by woodpeckers or inmanmade nesting boxes. The hen wood duck will investigateseveral cavities or boxes before choosing one for a nest site.

The cavities must be sufficiently large to allow the hen toenter and lay eggs, but not so large as to allow easy accessby predators. Cavities used by nesting wood ducks areusually more than eight feet above the ground and withinsight of a marsh, river, or lake. Typically, the cavity is locatedin a large, old tree.

In the early 1900s, wood ducks nearly vanished, due partly tothe extensive loss of old trees to logging. This left few placesfor wood ducks to nest. Loss of suitable nest sites, coupledwith unregulated hunting, led to extremely low populations.


Wildlife managers responded by closing wood duck huntingseasons and erecting nest boxes. Over time and as moreboxes were erected, the wood duck population recovered,and hunting was again allowed. The wood duck is so abun-dant in modern times that it typically is the second mostharvested duck in the eastern United States. The history ofwood ducks represents one of the greatest successes ofNorth American wildlife managers.

Nest boxes continue to aid wood duck populations in manyareas. Wood ducks will successfully nest in boxes that areproperly built and maintained. Those that are improperlybuilt or maintained simply go unused by nesting females. Orthey can allow predators to kill adults, eggs, and ducklings.You’ll learn more about nest boxes for wood ducks in thesection entitled “Management of Habitat.”

Wood ducks normally lay an egg per day until about 12 eggsare laid. Occasionally, more than one hen will lay eggs in thesame box or cavity, and as many as 40 eggs will accumulate.These large clutches are called dump nests. Hens sometimesabandon them because the large number of eggs makes itimpossible to incubate. Dump nesting tends to occur innesting cavities that are readily visible and areas with highdensities of wood ducks.

The pair bond between the male and female breaks downaround the time that the female lays the last egg and incu-bation begins. The female incubates the eggs alone andturns and moves the eggs daily to ensure that all eggs areproperly warmed. She also takes one or two short breakseach day to feed and drink. After about 30 days, the eggshatch. Upon hatching, the hen broods the young for another24 hours. The hen then exits the nest and calls to the brood.The ducklings respond by crawling out the opening anddropping to the ground or water below. Once all the duck-lings have left the nest, the hen leads the young to a securewater area where they can feed.

The young remain with the hen for the first several weeks.The female gradually spends more time away from the young.She eventually abandons them when they’re about five weeksold. The young are capable of flight by nine weeks of age.


During the summer, males join in flocks and undergo a wingmolt, which renders them flightless for about three weeks.After nesting, hens join up with these males to molt andremain flightless for three weeks. Adults and young arecapable of flight by late summer. They often concentrate inlarge flocks at traditional sites, such as wooded swamps.In northern areas, wood ducks usually migrate south bymid-October. In southern areas, they migrate little or not at all.

Wood duck young feed extensively on aquatic and terrestrialinsects, other invertebrates, and small fish that providethe protein needed for rapid body growth. As they mature,their diet changes to mostly plant material. Preferred foodsinclude small acorns of pin oak, seeds from bald cypresstrees, burweed, buttonbush, and fruit from wild grapes andmulberries.

Bay DucksIn North America there are five species of ducks from thetribe Aythyini. They all are important game birds and areoften found in flocks on large marshes, lakes, bays, andestuaries during winter. In the spring, many also use smallerponds and can be found paired or in small flocks. The mostcommon and widespread bay duck in North America is thelesser scaup.

Lesser scaup. These ducks (Figure 8) are medium-sizedand weigh about one and three-quarter pounds as adults.The male has a black head with a slight purple cast. Theneck, breast, and rump are black; the belly is white; and thesides and back are gray. Upon close inspection, the wingsand backs of males are actually marked with very fine wavylines, alternating in color between white and black. This pattern is called vermiculation.

Females are overall dark brown with a white or tan patch at the base of their bill and a white belly. In both sexes, the wing is dark with a white speculum. Both sexes have a blue-gray bill. Therefore, scaup are often referred to as“blue bills.”


Lesser scaup nest across a broad area of Canada andAlaska. They spend winters primarily on coastal areas of theUnited States and Mexico and are most prevalent along theGulf of Mexico. However, in winter they can also be found inflocks on almost any large marsh, lake, reservoir, or bay that’s not frozen.

Scaup are monogamous each breeding season. However,they form a new pair each winter or spring. There are fewerfemales than males, so many males have no mate. Somescaup attempt to nest in their first spring when they’re nearly one year old, but most don’t attempt to nest untiltheir second or third year.

Nest sites are usually on small islands or floating mats ofvegetation. Some nests are in upland sites. These sites areusually within 20 yards of water. The nests are generallyconcealed by vegetation. Nesting begins later than withmallards, usually not until the middle or later part of May.

Like many ducks, scaup lay one egg per day on most daysuntil the clutch is completed. The average clutch size isabout 10 eggs. Incubation begins after the last egg is laidand lasts about 25 days. Various predators—includingskunks, foxes, crows, magpies, and gulls—eat scaup eggs.The success rate of nests, that is, the percent of nests thathatch at least one egg, varies from area to area and year toyear. For scaup, nesting success is usually 5% to 50%. Thisrange is typical of most ducks who nest on the ground. Re-nesting sometimes occurs if a hen loses its nest to predation.

FIGURE 8—Male LesserScaup (Courtesy U.S. Fishand Wildlife Service)


The hatching process of the scaup is similar to that of mal-lards. The hen scaup broods her young for the first day afterhatching and then leads them to water areas to feed. Shecontinues to accompany them and lead them through themarshes until they’re three to five weeks old, at which timeshe abandons them. The young usually join up with otherabandoned young. When they’re about seven weeks old theycan fly.

Scaup gather at traditional molting sites and replace theirflight feathers in July and August. Hens that were successfulat breeding normally molt later in the summer than malesand unsuccessful females. Each bird is flightless for threeweeks or more.

The fall migration begins in September or October. Theyarrive on wintering areas during October through December.The fall migration is often accomplished in just a few longflights of up to 1000 miles. The birds tend to gather in flocksof 20 to 50 individuals. The spring migration tends to be prolonged. Some birds depart wintering areas as soon as theice begins to melt. Others delay their departure until May.

Scaup feed by diving to the bottom and finding food items.Their diet varies, but generally they consume more animalmatter than plant matter. Small clams, snails, other aquaticinvertebrates, and aquatic plant seeds are important foods.

Two other bay ducks offer interesting comparisons to lesserscaup: the greater scaup and the redhead duck.

Greater scaup. These ducks are closely related to lesserscaup. The two have very similar appearances. In fact, manyprofessional biologists have difficulty telling them apart.Compared to lesser scaup, greater scaup are slightly larger,have a green tint to their head, and have more white on theirwing tips. Greater scaup are also more common in oceanbays, whereas lesser scaup are more common in freshwaterhabitats.

Redhead ducks. The reproductive strategy of these ducks(Figure 9) is different than that of lesser scaup. Redheadhens often lay their eggs in the nests of other redheads orother species of ducks. This is termed parasitic nesting,because the laying hen relies on another hen to incubate her eggs. The most frequent species parasitized by redheadsis the canvasback.


Mergansers and Sea DucksThe Mergini tribe has 15 species in North America. Anotherspecies, the Labrador duck, disappeared from the coasts of eastern Canada around 1875 for unknown reasons.Unfortunately, the members of this tribe are only poorlystudied compared to most other North American ducks.Although this tribe is diverse, the common eider is a goodexample to use when discussing the group.

Common eider. This is the largest duck in North America,weighing three to five pounds when fully grown. The male is mostly black and white. Its breast, neck, and back arewhite. Its belly, rump, and top of head are black (Figure 10). Females aremostly brown. Both sexeshave large bills.

FIGURE 10—Common EiderMale (Courtesy Glen Smart/U.S.Fish and Wildlife Service Photo)

FIGURE 9—Male Redhead Duck (Foreground); Female(Background)


Common eiders can be found in coastal areas of Alaska,Canada, and the northeastern United States. They nest onrocky shorelines or islands and spend the winter along manyof the same northern coasts.

Common eiders are monogamous, selecting a mate eachwinter or spring. Occasionally, the same mate is selected inconsecutive years. They don’t form pair bonds until theirsecond winter or later. Nests are often concentrated ontraditional sites, such as islands. Nest sites are usuallyunder shrubs or among rocks that provide concealment.Clutch size is typically four or five eggs, and the incubationperiod lasts about 26 days. Some females will re-nest if theirnest is destroyed.

Upon hatching, the female broods the ducklings for the first24 hours and then leads them to nearby water. Despite theefforts of females to protect their young, the ducklings arevulnerable to gulls and other predators. Often several broodswill join together, resulting in flocks containing dozens ofducklings and several hens. The young are capable of flightwhen they’re between eight and nine weeks old.

Females remain with their young and molt their flight feathersduring the brood rearing period. The hens typically regaintheir ability to fly at about the time the young attain flight.Nonbreeding females and males usually leave nesting areasin summer and fly to traditional molting areas. They’reflightless for several weeks.

Common eiders feed extensively on blue mussels, a type ofmarine clam. They also feed on sea urchins, a type of spinystarfish, and other marine invertebrates.

The mergansers and sea ducks are a diverse group. Somespecies in this tribe nest in tree cavities, others on theground, and others in rocky crevices. Some use mainlyfreshwater habitats, whereas others use mainly marinehabitats. Some are specialized to feed on fish, whereasothers—such as the common eider—feed mostly on clams.

Stiff-Tailed DucksIn North America, the ruddy duck and masked duck are theonly two species from the tribe Oxyurini. Masked ducks arefound mainly in South America, with only small numbers in the Caribbean Islands, Mexico, Texas, and Florida. Theruddy has a wider distribution across North America and ismore abundant throughout.

Ruddy duck. This duck is small and stocky, with a shortand thick neck (Figure 11). It weighs about one and one-fifthpounds when fully grown. Males in breeding plumage haveblue bills, white cheeks, black caps, and red-brown backsand sides. In the fall and winter, males are drab-brownexcept for the white cheek and dark cap. Males will oftenhold their tail feathers erect and out of the water. Femalesare mostly drab brown and gray, with a light and dark stripebelow each eye. The wings are entirely dull-brown in bothsexes.

Ruddy ducks nest mainly in the Prairie Pothole region ofNorth America and winter primarily in southern coastalmarshes. They can be found in a variety of wetland types,ranging from small marshes to large lakes and estuaries.

Ruddies are monogamous but find a new mate each year.Some breed in their first year, whereas others delay breedinguntil their second or third years.


FIGURE 11—Male RuddyDuck (Courtesy U.S. Fish and Wildlife Service)


Ruddies nest on mounds of vegetation that they construct in shallow marshes. Like the redhead, ruddy ducks can be a parasitic egg layer, depositing eggs in the nests of otherruddy ducks or other species. Their eggs are considered verylarge for the size of the female. Usually 8 eggs are laid, andincubation lasts for about 24 days. Re-nesting may occurwhen a nest is lost to predation.

Brood rearing behavior is variable with ruddy ducks.Generally, only the female accompanies the young. However,occasionally both parents will. Sometimes neither parent will accompany them. The young can fly once they’re betweensix and seven weeks old. The adults apparently molt theirflight feathers in summer, but this isn’t well documented.

Ruddy ducks dive to feed. They eat mainly plant matter, preferring the seeds and leafy parts of aquatic plants. Theyalso consume aquatic invertebrates, including insects andsmall clams.

GeeseIn North America there are seven species of geese.

Canada geese. This species is the most widespread andnumerous (Figure 12). Many people mistakenly call them“Canadian geese.” This is inaccurate because it would meanthat the geese are actually from Canada, which isn’t always

true. Males are called ganders, females simply geese, and the young goslings.

FIGURE 12—(A) CanadaGeese; (B) Canada Goose and Goslings (A: Courtesy of Wyman Meinzer/U.S. Fishand Wildlife Service Photo)

A

B


Physical characteristics. Both sexes of Canada geese appearsimilar. They have black necks and heads, except for a whitecheek patch (Figure 13). Their backs are brown or gray,chests light gray or tan, and tails black. Their bills and feetare also black. The wings are dark brown and black.

Most biologists recognize about 11 subspecies or races ofCanada geese. They vary widely in size from the cacklingCanada goose, which is only about 3 pounds and slightlylarger than a mallard, to the giant Canada goose who weighsup to 12 pounds.

Range. Canada geese can be found throughout Canada andthe continental United States. It’s interesting that the smaller subspecies nest farthest north, often along theshores of the Arctic Ocean. They also winter farthest south,often in places such as Texas.

The larger subspecies nest farther south—including much of the United States—and winter in their nesting area or onlyslightly farther south. Thus, the large subspecies migratesmall distances between breeding and wintering areas,whereas the small Canada geese migrate thousands of miles.

FIGURE 13—CanadaGeese: Male and Female with Goslings


Mating/nesting. Canada geese—like other geese—aremonogamous. Their pair bond lasts for life. When one matedies, the surviving bird will form a new pair bond. The birdsnormally pair when they’re one or two years old. Most don’tattempt to nest until their second spring or later.

Canada geese will nest in a large variety of sites, but mostprefer to nest on small islands or close to water. Females will often return to the same nest site in successive years.They normally lay about five eggs. The females incubate theeggs for about 27 days while the gander stays near and alertfor predators. The female takes one or two short breaks each day of incubation to feed and drink. Re-nesting rarelyoccurs in northern nesting areas, but occasionally occurs in southern areas.

The female broods her goslings for the first 24 hours afterhatching. Both parents then accompany the brood. The gander remains alert for predators. This wariness permits thefemale and young to feed extensively. The goslings grow rap-idly and are capable of flight by the time they’re about 6 to 10weeks old. Smaller subspecies require the least time to fledge.

The birds remain in family groups throughout the broodrearing period. In fact, the family group typically remainstogether until the following spring when the adults againattempt nesting. Some one-year-old geese will rejoin theirparents, even when the parents have a new brood.

During the brood rearing period, the adults molt their flightfeathers. By the time the young can fly, the adults havegrown new feathers and again can fly. This flightless periodusually occurs in July. Nonbreeding adults often will migrateto large marshes—sometimes hundreds of miles away—where they’ll gather with other geese and molt.

Migration. Migration out of breeding areas occurs inSeptember in the North. However, in nesting areas that arelocated farther south this migration is delayed. Migratingflocks typically fly as high as 8000 feet—often in a large “V”formation of several hundred geese. They often make longflights that take them several hundred miles in a day. Somefly immediately to wintering areas, whereas others delaytheir arrival until later.


In wintering areas, Canada geese remain flocked. They typi-cally spend the day on large bodies of water and make flightsto feeding areas at dawn and dusk. As the weather warms,they migrate northward at a pace equaling the timing ofspring thaw.

Diet. Canada geese are herbivores. They’ve adapted to farm-ing and readily eat many grains, including corn and soybeansand the green leaves of alfalfa, wheat, and rye. They also eatwild plants, including the leaves and roots of wetland plants.

Population numbers. Most goose populations have thrivedwhen hunting is regulated. In many urban areas, hunting isimpossible. Canada goose populations have grown so largethat they’ve become a nuisance.

Snow geese. These geese (Figure 14), who nest in concen-trations in the arctic, are also so numerous that they’redamaging their food resources on the nesting grounds. Aninteresting point regarding snow geese is that they have twocolor phases. Some are nearly all white, whereas others are adark blue and hence are called “blue geese.” These two colorphases are both the same species.

SwansThree species of swans are found in North America: trumpeterswan, tundra swan, and mute swan. They all are large whitebirds with long necks.

FIGURE 14—Snow Geese


Differences among the species are subtle. The mute swanhas an orange bill with a black knob (lump) and weighsabout 25 pounds as an adult. This swan often holds itswings slightly above its back while swimming. The trumpeterswan has a black bill and weighs 21 to 38 pounds. Thetundra swan also has a black bill. This swan is the smallest,weighing 12 to 19 pounds.

The black bills of tundra swans often have a yellow spot attheir base. Tundra and trumpeter swans hold their wingsflat on their back when swimming. Male swans are calledcobs; females are called pens; and the young are referred toas cygnets. The cygnets of all three species are light grayuntil they’re one year old.

The mute swan (Figure 15) was introduced into NorthAmerica from Europe. It’s now found in many places acrossNorth America, especially along the East Coast. Tundraswans (Figure 16) were previously called “whistling swans.”They’re the most abundant of the three species. Trumpeterswans (Figure 17) were nearly wiped out in North America,but their population has gone through a dramatic recoveryin the last 50 years. The biology of trumpeter swans is gen-erally representative of all species.

Trumpeter swans formerly nested over much of Alaska,southern Canada, and the northern United States. Excessivehunting nearly eliminated them from the continent. Protectionfrom hunting and re-introductions of pairs to suitable areashave allowed the population to recover. They’re now commonin the interior of Alaska and can also be found at many loca-tions in the Rocky Mountains, Canada, the West Coast, andMidwest. They winter along the Pacific Coast of Canada andAlaska and at scattered other locations throughout theUnited States.

Trumpeter swans—like all swans—are monogamous andform lifelong pair bonds. They pair when they’re three yearsold or older, but don’t usually attempt nesting until theirfourth year. Nests are built of aquatic vegetation in shallowwetlands. Pairs vigorously defend a nest site from otherswans. A clutch size is usually four or five eggs. Incubationlasts about 35 days. The female incubates the eggs while themale remains near.


FIGURE 15—Mute Swan

FIGURE 16—Tundra Swan

FIGURE 17—Trumpeter Swan


Pens brood their cygnets for the first 24 hours after hatching. The cygnets remain with their parents in a familyunit. When cygnets are 14 to 17 weeks old, they’re capableof flying. Adults undergo wing molting during the summerand are flightless for about 4 weeks. The family unit remainsintact throughout the fall and winter. One-year-old birds willoccasionally remain with the parents, even when they have anew brood.

Cygnets feed on aquatic invertebrates and the vegetation of wetland plants during their first few weeks. Their dietchanges by the time they’re fledged. Then they eat only wetland plants.


Self-Check 21. What does an adult male mallard look like?

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2. Define the term brooding and explain its purpose.

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3. What do scientists call young ducks, young geese, and young swans?

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4. Name two North American waterfowl species that pair for life.

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5. Which species of duck was nearly wiped out in North America but is now abundant in the East?

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BASIC BIOLOGY

ReproductionAmong waterfowl there’s variation in characteristics of repro-duction, such as duration of pair bonds, age at breeding, andclutch size. However, there also are similarities. Like otherbirds, the eggs of waterfowl are fertilized internally in thefemale, before the eggshell is deposited around the egg. Theact of mating, or copulation, is the process by which sperm(male sex cells) are transferred from the male to the female.

Waterfowl pairs mate on the water. The male climbs up ontothe back of the female and grasps her on the neck with hisbill. He then briefly inserts his penis—the male sex organ—and transfers sperm into the female’s cloaca, a commonopening for the reproductive, digestive, and excretory tracts.Mating occurs about once per day during the egg-laying period.

Once incubation begins, the female uses her bill to turnthe eggs daily. The eggs are rotated from one side to theother and rearranged in the nest bowl. This rotation ensuresuniform incubation of each egg as well as the entire clutch.

Females pluck down feathers from their breast and gradu-ally line the nest bowl during egg-laying and incubation(Figure 18). When the female leaves the nest, she covers theeggs with the down feathers. Upon returning, she uncoversthem before sitting down on the eggs.

Because she has little or no down feathers on her breast, the female rapidly and efficiently incubates the eggs with herwarm and nearly naked breast. By covering the eggs withdown feathers, she insulates the eggs from cold temperatureswhile she is absent. The eggs are easily warmed again oncethe female returns. Covering the eggs also helps to conceal them from predators.

If a female re-nests, there are usually few down feathers inthe nest because she has used them all in the earlier nestingattempt. The female’s down feathers do grow back in time.


The daily breaks from incubating allow the female to feedand provide important moisture to the developing eggs. Thefemale’s breast feathers become wet when she is swimmingand feeding. This moisture is deposited on the eggs whenshe returns to the nest. If the eggs aren’t periodically mois-tened, survival diminishes because it becomes difficult forthe young to hatch due to dry, hard shells.

NutritionDiet. The diet of waterfowl is highly variable, sometimeseven within a single species. For all species of waterfowl,consumption of adequate amounts of energy (calories) andprotein is important. Protein is needed for growth of muscles,feathers, and other tissues. It’s most critical during their

FIGURE 18—A Canadagoose nest is lined withdown feathers from thefemale. (Courtesy Bureau of Reclamation; U.S.Department of the Interior)


first few weeks of life, when the young are growing rapidly.It’s also important during

• Molt, when new feathers are growing

• The nesting season, when females are growing eggswithin their reproductive tract

Waterfowl acquire protein from various sources. Animalfoods—such as fish, crustaceans, snails, earthworms, andaquatic insects—generally have high protein content. Thetips of most growing plants also have high protein content.Waterfowl store some protein in their body as muscle.

Energy. Waterfowl use energy for activities such as swim-ming, flying, or bathing. Even when they’re inactive,waterfowl require energy for breathing, maintaining circula-tion and a constant warm body temperature, and otherinternal processes.

Despite the excellent insulating qualities of feathers, water-fowl burn more energy during colder weather. For example,an average-sized Canada goose requires about 15% moreenergy to survive when the temperature is 30°F comparedwith when the temperature is 60°F.

Some activities are more strenuous and burn more energythan other activities. The least amount of energy is neededduring sleep. By monitoring the heart rate of waterfowl, biologists have determined that swimming requires about 2.3 times as much energy as sleeping, whereas feedingrequires 2.8 times as much energy as sleeping. Flyingrequires the most energy, approximately 11 times as muchenergy as sleeping!

Foods that have a high energy content are generally seeds,grains, and some animals. Waterfowl store energy reserves in their body as fat and muscle.

Ducks and geese have different strategies for meeting theirnutritional needs during the nesting season. Female ducksfeed heavily during the winter months on seeds and grainsand build up large fat deposits. During the nesting season,they change their diet to mostly small invertebrates thatyield lots of protein but only little energy. They burn fatreserves to meet their energy needs and obtain the proteinfor egg production through feeding.


Geese feed heavily on grains during the winter, and thisbuilds fat reserves. During spring migration they feed exten-sively on the spring growth of grasses that are high in proteincontent. By the time geese have completed their migration to nesting areas, they have large deposits of both fat andmuscle. Once nesting begins, geese feed little and rely mostlyon body reserves to produce eggs and provide energy foractivities.

Molting and PlumageThe process of shedding and growing new feathers is calledmolting. All feathers on waterfowl are replaced at least onceper year with new feathers. When first hatched, waterfowlhave only downy feathers. This first plumage, or coat offeathers, is the natal plumage (Figure 19).

The rigid body feathers, called contour feathers, begin grow-ing soon after the waterfowl hatch. By the time they can fly,waterfowl have a new layer of down feathers covered by alayer of contour feathers. The down feathers are excellent for insulation, whereas the contour feathers serve manyfunctions. The large contour feathers of wings are necessaryfor flight.

On male ducks, the contour feathers are bright and helpthem attract a mate. On females, the contour feathers provide concealment during nesting. Contour feathers are

FIGURE 19—Duckling in Its Natal Plumage of DownFeathers


waterproof. This is a characteristic that allows the downfeathers beneath them to remain dry and retain their insulating qualities.

Plumage with both contour and downy feathers is calledjuvenile plumage. Eventually, the juvenile feathers arereplaced, usually beginning around late summer. The newfeathers actually push out the old feathers. While they’regrowing, blood is supplied to the feather. When these feath-ers are plucked, a small spot of blood will often be seen.Hence, growing feathers are often called blood quills. Afterthe feathers have fully grown, the blood supply ends. Thesefeathers leave no spot of blood when plucked.

Some feathers on ducks are replaced twice per year. In fact,for a time during the summer adult males look similar tofemales! This is called the basic or eclipse plumage. The contrasting plumage seen during the rest of the season iscalled the alternate or breeding plumage (Figure 20). Femalesalso have both basic and alternate plumages, but they havesimilar appearances.

A

B

FIGURE 20—(A) Male Mallard Plumage:Breeding Plumage; (B) Male MallardPlumage: Basic Plumage (Courtesy U.S.Geological Survey)


The flightless period that adult ducks have occurs during themolt before the basic plumage grows in. This is called theprebasic molt (Table 2). Mallards remain in the basicplumage for only a few weeks. Other ducks—such as blue-winged teal and ruddy ducks—remain in the basic plumagethrough winter.

June

July

August

September

Fall

Winter

Spring

June

July

August

September

Fall

Winter

Spring

Juvenile Plumage

Hatch, NatalPlumage

Prebasic Molt

Basic Plumage

Pre-alternate Molt

Alternate Plumage

Prebasic Molt(Flightless)

Basic (Eclipse)Plumage

Pre-alternate Molt

Alternate Plumage

Juvenile Plumage

Hatch, NatalPlumage

Prebasic Molt

Basic Plumage

Prebasic Molt(Flightless)

Basic Plumage

Table 2BREEDING CHARACTERISTICS OF MALLARDS

AND CANADA GEESE*

Time Mallards Canada Geese

*Dashed lines represent molts; solid lines represent plumages.


After the basic plumage grows in, ducks go through the pre-alternate molt. In the prealternate molt, nonflight feathersare replaced. These nonflight feathers are most of the feathersof the body, head, and neck, but not those on the wings andtail. Then the ducks enter into their alternate plumage.Ducks can continue to fly during the pre-alternate moltbecause they don’t shed their wing feathers. This plumagecycle continues annually for ducks.

Geese and swans have no alternate plumage and no pre-alternate molt. They progress from the juvenile plumagethrough a prebasic molt and into the basic plumage. Then,every year they molt their feathers only once and remain inthe basic plumage. The prebasic molt is extended over severalmonths, although the wing feathers are replaced in latesummer. The basic plumage appears similar in both malesand females. Once they’re one year old, the molting cyclecontinues on an annual basis in geese and swans.

MigrationMost North American waterfowl migrate between winteringand breeding areas. Migration probably evolved so that thebirds can take advantage of seasonally changing conditions.

The summer season in the North is a perfect place for rais-ing young waterfowl. Temperatures are moderate, day lengthis very long, and aquatic insects and other foods are usuallyabundant. However, by autumn temperatures drop. Thesenorthern areas freeze and become snow covered. Thus thebirds must move south to find milder temperatures andareas where they can feed.

Some North American waterfowl migrate thousands of milesbetween breeding and wintering areas. Pintails banded inAlaska have been found shot by hunters in Guatemala. Theirmigration took them nearly 5000 miles.

Wild geese who nest in southwest Alaska fly over the PacificOcean to their wintering areas in California and westernMexico. This is an amazing flight of approximately 2000 to3000 miles, mostly over the open ocean!

Hormones produced in the body of waterfowl cause theirurge to migrate. Photoperiod, or length of daylight, regulates


these hormone levels. The precise moment of migration iscontrolled more by weather conditions. The birds normallybegin a migratory flight when the wind is blowing in thesame direction that they want to migrate. In the fall, thisusually occurs with advancing cold fronts. In the spring,migration often occurs with advancing warm fronts. In bothspring and fall, migratory flights normally begin at sunset.

During migration, waterfowl fly at a speed of about 50 milesper hour, but their speed can be greatly increased with astrong tailwind. Most fly several thousand feet high. However,they can also fly high enough to pass over 10,000-footmountains. However, sea ducks fly only several feet abovethe water during migration.

Waterfowl have several adaptations that allow them to navi-gate thousands of miles during migration. Through elaborateexperiments, biologists have determined that waterfowl use

• An internal biologic clock

• Patterns of stars

• The position of the sun and moon

• The earth’s magnetic field

• Landmarks

Their ability to navigate on cloudy nights—when stars andlandmarks are invisible—is mostly dependent on their abilityto sense the earth’s magnetic field. Most of their ability tonavigate is innate, which means that they’re born with it.However, recognition of key landmarks is probably learnedfrom one generation to the next.

Some waterfowl—especially geese and swans—often migratein distinct “V” formations or long lines. In this formation, thelead bird breaks the wind and makes it easier for birds fol-lowing behind to fly. The exact spacing between birdsminimizes the amount of energy that each bird needs to fly.


Field Characteristics of Age and SexWaterfowl managers often measure the success of theirefforts by determining the number of young that survive to autumn. They compare the number of young to the num-ber of adults in the harvest. Managers are also interested in knowing how many males and females are present in anarea. To determine any of these measures, one must be ableto distinguish young birds from adults and males fromfemales.

Sex. Distinguishing the sex of most ducks during the fall orwinter is easily accomplished by examining the plumage.However, when the birds are very young or they’re in eclipseplumage, the sexes aren’t obviously different. Also, the sexesaren’t easily distinguished in whistling ducks, geese, andswans. In these cases, the best way to identify the sex is byexamining the cloaca (Figure 21).

In males, a penis will be present. The penis is located to theleft of center and at the bottom of the cloaca (about 8 o’clockposition) when the bird is held upside down, with its tailtoward you. In birds who are less than 1 year old, the penisis small—usually less than one quarter inch long. In olderbirds, the penis is larger and may be twisted and bumpyduring the breeding season. In the nonbreeding season, thepenis is usually enclosed within a sheath.

On some waterfowl, a clitoris (female sex organ) can be foundon adult females. The clitoris is located at the 12 o’clockposition when the bird is held upside down with its tailtoward you. In adult female Canada geese, the length of theclitoris is about one-half inch. Internal examinations canalso be used to determine the sex of waterfowl.

Age. The age of waterfowl is usually classified as young(less than one year old) or adult (one year or older). If theyoung are still in their natal plumage, then age is obvious.Otherwise, the age isn’t obvious for most species. The excep-tion is for swans, which mostly have gray feathers whenyoung and white feathers as adults.

In other species, age can be determined by examining tail orwing feathers. For instance, in mallard young, the tip of thetail feathers will have a small V-shaped notch. The adult tail


feathers have a pointed tip. For geese, the wing tips of youngbirds tend to be sharply pointed, whereas those of adultstend to be more bluntly pointed. The age of ducks can bedetermined by examining their wings, because wing charac-teristics differ among ages. However, these characteristicsalso differ among species.

Age can also be determined by examining the size of thepenis in males. With females, experts can determine age byclosely inspecting the cloaca.

Population DynamicsWaterfowl are normally managed as a population. A popula-tion is a group of organisms of the same species in a givengeographic area. Examples of waterfowl populations includemallards in North America or trumpeter swans in Michigan.Occasionally, managers will group species together and referto them as a collective population, for example, the seaducks of the Chesapeake Bay.

FIGURE 21—Relative Size and Position of the Penis (Male) and Clitoris (Female)in the Cloaca of Canada Geese

Adult Male(Penis in Sheath)

Adult Male(Penis out of Sheath—Breeding

Condition)

Immature Male Female


Population Size

The most critical measure of a population is usually thenumber of individuals. Wildlife managers have establishednumeric goals for many waterfowl populations. They deter-mine how successful their actions have been by comparingpopulation estimates to population goals.

The size of waterfowl populations changes over time. Newindividuals who are hatched increase the size of the popula-tion, whereas those who die reduce the population.

Some new individuals may travel into the area and join thepopulation. This is immigration. Other individuals may leavethe area. This is called emigration.

Birth and Death Rates

Waterfowl biologists are usually most concerned with thebirth and death rates. These rates are normally estimated forone-year time periods. The birth rate is usually expressed asthe number of new individuals produced per adult female (oradult). The death rate is usually expressed as the proportionof a population dying during a year.

Birth rate. This rate is controlled by many factors, includ-ing clutch size, re-nesting attempts, fertility of eggs, andweather. In larger clutches, the number of young hatchedtends to be higher. If food is abundant during the egg-layingperiod, then female ducks can lay many eggs. Also, with agood food supply the females are more likely to re-nest iftheir first nest is destroyed.

Female geese and swans tend to lay larger clutches and havebetter success hatching their eggs when they have large fatand muscle deposits in their bodies. Because not all eggsbecome fertilized, they don’t all hatch. In wild mallards,between 1% and 3% of the eggs are infertile.

Weather. This factor can be an important influence on thebirth rate. If eggs are covered with water, the developingembryos are chilled and die. Thus, flooding can reduce thebirth rate. Late spring snow and ice storms can also freezeeggs.


Predation. Generally, the birth rate of ducks is controlledmostly by predation. This is particularly true for those ducks who nest in upland sites, as the dabbling ducks do.Although female ducks generally select concealed spots tonest, predators are very adept at locating nests. Once found,the hen doesn’t attempt to defend her eggs.

The predator list for duck nests is long. It includes manyfamiliar species, such as skunks, raccoons, foxes, opossums,minks, weasels, ground squirrels, crows, magpies, gulls, andsnakes (Figure 22).

Predation on nests tends to be highest when predators are abundant and nesting cover is sparse or of poor quality.When nesting cover is sparse—such as in intensively farmed areas—the females tend to nest along roadsides and fencerows. Predators frequently roam these places and discover the nests.

FIGURE 22—Gulls andblack rat snakes aresome of the predators of waterfowl nests.


Predators have a more difficult time finding nests located in large fields or pastures. In fields where the vegetation is extremely short—that is, less than about four inches—predators can easily move about and find hens or nests. In fields with taller vegetation, predators are less apt to findnests. Therefore nesting success is higher in this latter situ-ation. When more than about 15% of mallard nests hatch,the population normally will increase. When less than 15%hatch, the population usually declines.

Farming practices. This factor also destroys nests and can be an important limitation on the birth rate in someareas. Ducks will often nest in hay fields. The nests will bedestroyed when the hay is cut, raked, or baled. However,some ducks will begin nesting early enough to hatch beforethe first hay crop is cut. Others who nest after the first cut-ting will have their eggs hatch before the second cutting.Other nests may be destroyed when fields are plowed orplanted.

Death rate. This rate varies among populations, ages, andsexes. Usually, between 20% and 30% of the individuals in goose and swan populations die each year. For ducks,between 30% and 65% die annually. Generally, the youngare at greater risk of dying than are adult waterfowl. Causesof mortality vary.

Predators kill large numbers of waterfowl—especially thosethat are young or weak. These predators include hawks,owls, eagles, gulls, mink, weasels, raccoons, foxes (Figure 23),coyotes, fish, turtles, and even alligators. The greatest risk towaterfowl occurs within the first few days after hatching.

With upland nesting ducks, predators sometimes take entirebroods when the hen is attempting to lead them over land tothe security of a marsh. Gulls can be very efficient predatorsof eider ducklings. In extreme cases, all the young from acolony may be eaten within the first few hours after hatching.As the young grow and are able to fly, they become less vul-nerable to mammalian predators. However, hawks, owls, andeagles continue to kill some.

Hunting. This is another form of predation that kills a vary-ing proportion of the waterfowl population, depending on thespecies, area, and year. Mallards are one of the most popular


hunted species of waterfowl. In North America, about 5% to 20% of the mallard population is harvested by hunters inany year.

The harvest rate (proportion of a population killed yearly) formallards is about 1.4 times higher for birds less than 1 year old compared to adults.

A higher proportion of drakes are shot compared to the pro-portion of hens, probably because hunters intentionallyselect drakes when given a choice. In addition to the birdsactually shot and harvested, some birds are shot but neverfound by the hunters. This is called crippling loss. About20% of the birds that are shot are never recovered.

Other causes of mortality. Weather can kill waterfowldirectly. Or it can weaken them and make them vulnerableto disease or predation. Young waterfowl who haven’t yetgrown all of their contour feathers can be killed throughhypothermia (lowered body temperature) during extendedperiods of cold or rainy weather.

Even adult waterfowl can die due to starvation or hypother-mia during harsh weather. Occasionally, diving ducks willstarve to death when they fail to leave a marsh before itfreezes. Without large areas of open water, these ducks can’t get airborne, and hence they’re trapped. Once thewater freezes completely, they’re unable to feed.

FIGURE 23—The fox is another predator of waterfowl.


Most waterfowl who die from diseases go unnoticed. The sickbirds will become inactive and hide in thick cover. Once theydie, they may be scavenged by other wildlife. Thus, humansmay never notice their carcasses. Occasionally, a contagiousdisease outbreak will result in the rapid and obvious deathof a large number of waterfowl. These outbreaks usuallyoccur in places where

• Birds are concentrated in a small area

• Birds are stressed due to extreme hot or cold weather

• A history of disease outbreaks exists

Avian cholera. This disease is caused by a bacterial infec-tion. Cholera usually occurs during winter in areas wherethere’s a history of cholera outbreaks. Infected birds may diewithin 6 to 12 hours of contracting the disease. They’relethargic (inactive) or have convulsions shortly before death.Death occurs because of tissue destruction in major organs.The bacteria multiply in sick birds and are passed from onebird to the next. One of the largest outbreaks occurred onthe Chesapeake Bay in 1978 when nearly 100,000 scoters (a type of sea duck) died.

Botulism. This disease is also caused by a bacteria. Birdsencounter the bacteria in stagnant wetlands during the sum-mer. The bacterial infection causes paralysis, and the birdsoften die by drowning because they can’t keep their headsout of the water.

The carcasses of dead birds (Figure 24) become infested withfeeding maggots (fly larvae) that eat the rotting flesh. Thesemaggots in turn harbor the bacteria, which is then passedon to other waterfowl when they eat the maggots. Over onemillion waterfowl died during a large outbreak of botulism in Utah and California during the summer of 1910.


Lead poisoning. This condition is another waterfowl disease.However, it’s not contagious.

Lead poisoning is caused when waterfowl eat spent lead shotor occasionally when they consume discarded lead fishingsinkers. The waterfowl eat the shot thinking that it’s grit(sand or small stones), which is part of their normal diet.Grit is retained in the gizzard—the muscular part of a bird’sstomach—and is used to grind up seeds and other foods thathave also been swallowed.

Once lead shot is ground up in the gizzard, the lead isabsorbed into the body. The lead interferes with normaldigestive processes, and the bird slowly starves to death. As few as two or three swallowed pellets can kill a duck.Beginning in 1991, all waterfowl hunters in the UnitedStates were required to use steel or other nontoxic(non-poisonous) shot. Gradually, the amount of lead shotavailable to feeding waterfowl has diminished. Today leadpoisoning is much less common than it once was.

Accidents. Waterfowl also die from various accidents. Theseaccidents usually involve flying into an object—such asfences, utility lines, radio towers, or even buildings. Vehiclessometimes strike waterfowl—especially the young—whenthey walk across roads. Farm machinery occasionally killshens and their young who nest in fields. Commercial fishingnets entangle and drown waterfowl—especially bay and seaducks. Sometimes aircraft kill waterfowl.

FIGURE 24—Duck Carcassesafter an Outbreak of Botulism(Courtesy Dave Fruge/U.S.Fish and Wildlife Service)


Self-Check 31. How do waterfowl mate?

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2. List three times during the life of waterfowl when protein is needed in large amounts.

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3. Name the four plumages of ducks, beginning with the first phase.

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4. What triggers the urge for waterfowl to migrate?

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5. Explain three ways to determine the age of a male mallard.

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6. What waterfowl disease has been reduced by regulating the type of shot shells thathunters use?

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MANAGEMENT OF HABITATHabitat is the environment in which an organism or popula-tion lives. For a typical mallard in summer, its habitat wouldinclude all the marshes, lakes, rivers, and upland sites thatit might visit. All habitats are different, and some are betterable to meet waterfowl needs such as food and cover.

For example, a shallow marsh with a fringe of wetland vege-tation might be an excellent place for mallards to feed, butby itself the marsh would provide little or no place for themto nest. An adjacent grassy field would provide excellentnesting cover, but little food. Each of these habitats alonewouldn’t provide for all of the needs of nesting mallards.However, together they’d be an excellent nesting habitat.

Limiting FactorsThe size of a population in an area is often limited by somefactor of the habitat. A wooded swamp might have only 10 tree cavities that are suitable for nesting wood ducks.Therefore, even if 20 pairs of wood ducks lived in the marsh,there would be only enough habitat for 10 pairs to nest. Inthis example, availability of nesting cavities would be a limit-ing factor. The area would have only enough resources tosupport 10 wood duck nesting pairs.

The size of the population that a habitat can sustain iscalled its carrying capacity. If managers added 20 nest boxes to the marsh, then availability of nesting cavitieswould no longer be a limiting factor to the size of the woodduck population.

Another habitat factor then becomes the limiting factor.Perhaps there’s only enough food in the marsh for 15 pairsand broods of wood ducks. In this case, the carrying capacitywould then be 15 pairs and broods, and the limiting factorwould be food for the ducklings. Whenever one limiting factor is eliminated, another factor replaces it to limit thepopulation.

Habitat management is perhaps the single greatest aspect ofwaterfowl management. To be effective at managing habitat,you must first understand what factors are limiting water-fowl populations. Once the limiting factors are identified,habitat managers then manipulate the habitat to remove thelimiting factors and thereby increase the carrying capacity.

Habitat Management TechniquesAcross much of North America, nesting habitat is believed to be limiting populations of many dabbling ducks. Severaltechniques are available for improving the quality and quantity of nesting habitat. The feasibility of each techniquevaries.

Increasing the food source. One approach that’s oftenused is the purchase of land for planting of vegetation pre-ferred by upland nesting ducks. The most preferred vegetationis native prairie grasses—those plants that were originallyhere before human settlement—such as big bluestem, littlebluestem, Indian grass, and switchgrass. Managers maintainthe grasses in a healthy and vigorous state by mowing orburning the dead vegetation periodically (once every three tofive years). When it’s not possible to plant or maintain nativegrasses, then existing vegetation should be mowed or burnedperiodically to ensure that it doesn’t become too dense.

Creating nesting islands. Waterfowl tend to have highersuccess at hatching clutches when they nest on islands. Thisis because most mammalian nest predators won’t swim outto an island in search of food.

In some areas, managers have greatly increased the avail-ability and quality of nesting habitat by creating islands inmarshes. These islands can be less than one acre in size andstill accommodate many nesting ducks and geese. The bestislands are seeded with native grasses and have rocky shore-lines to minimize erosion from wave action. Gadwalls (grayish brown, medium-sized dabbling ducks), lesser scaup,and Canada geese are most often attracted to islands fornesting.



Another approach is to create miniature floating islands.These are constructed of wood platforms with secured flota-tion devices, such as foam blocks or sealed plastic pipes.Nesting material such as straw is provided. The platformsare anchored away from shore where they’re safe from mam-malian predators. If platforms aren’t maintained annually,they’ll lose their attractiveness to nesting waterfowl.

Wire baskets or cones erected on poles can also serve asminiature nesting islands. They can increase available nest-ing sites for mallards and Canada geese. The baskets shouldbe two to three feet above the high watermark and musthave adequate nesting material secured to the basket. Thebaskets should be maintained annually, usually in late win-ter. The erection of nesting cones is considered to be one ofthe most cost-effective methods for increasing the success ofnesting mallards.

Nesting boxes. Wood ducks, hooded mergansers, and sev-eral other species of waterfowl who nest in cavities will alsonest in constructed boxes. If nesting cavities are the limitingfactor, then erection of boxes will increase the size of thelocal breeding population.

Typical boxes are constructed of wood of three-quarter-inchthickness. They should be at least 10 inches wide, 10 inchesdeep, and about 24 inches tall. The opening should be nearthe top and ovate or elliptical in shape. This opening shouldbe 4 inches wide and 3 inches tall. An opening that’s toosmall won’t be used because the hen won’t fit in.

On the other hand, openings that are too large permit rac-coons and other larger predators to easily enter the cavity.The bottom of the box should be filled with three to six inchesof wood chips or sawdust, which will be used as nestingmaterial. The inner surface of the wall between the openingand the floor should be rough or covered with hardwarecloth (zinc-coated steel mesh). This is critical, because theyoung ducklings need a rough surface to cling to as theycrawl out of the nest. Nest boxes should be placed at leastfour feet above the ground or water on sturdy poles or trees.

The boxes should generally be located within site of a wetlandwhere it will be suitable for broods to feed, such as a woodedswamp. The box design should include a lid or wall that can


be easily opened to allow for annual cleaning. The cleaningshould be done each winter. Unhatched eggs, eggshell frag-ments, and nesting materials from other birds and animalsshould be removed. Any repairs to the box should also beconducted in the winter (Figure 25).

Other birds, squirrels, mice, bees, and wasps will also usethese boxes. Boxes that aren’t used by wood ducks or otherdesirable wildlife for several consecutive years should bemoved to another location. Eggs that have successfullyhatched in boxes will have leathery membranes attached tothe shell fragments. Down feathers from adults will also befound in successful nests.

Predator control. All of these approaches for improvingnesting success have focused on providing nesting sites thatare relatively safe from predators—especially mammals.Another approach that has had some success in local areasis predator control. This often requires special governmentpermission if it’s conducted outside of regular trapping andhunting seasons. Predator control is accomplished by inten-

FIGURE 25—Checking theCondition of a Nesting Boxfor Wood Ducks (PhotoCourtesy U.S. Fish andWildlife Service)


sively trapping an area just before—and even during—thewaterfowl nesting season. The trapped predators are eitherkilled or moved to another area.

Another method is to poison chicken eggs and then to placethese eggs in areas where nest predators are likely to befound. Predator control normally provides some immediateimprovement to waterfowl nesting success. However, rarelycan all predators be removed from an area. Sometimes nontarget animals—such as pets or endangered species—arekilled during predator control efforts.

The benefits of predator control are normally only short-term. In other words, predators will quickly repopulate anarea as soon as the efforts to remove predators end. The bestplace to employ predator removal is on islands, where it’smost difficult for predators to repopulate the area.

A more lasting way to control predator numbers is by makingthe habitat unsuitable for them. This can be accomplishedby eliminating their den sites, such as abandoned buildingsand large rock piles. Often, old buildings can be burneddown. Their foundations should be buried. Rock piles canalso be buried.

Increasing moist soil plant growth. At wintering andmigration areas, wetland foods are often the most limitingfactor for waterfowl populations. Generally, the plants thatproduce the highest quality and quantity of seeds for feedingwaterfowl are those that grow on mud flats in the summer.This group of plants is called moist soil plants and includesnumerous species. The most common moist soil plants arethe smartweeds (Figure 26) and wild millets (Figure 27), bothof which provide excellent duck food.

The key to growing moist soil plants is the ability to controlwater levels. Generally, water levels in marshes should bedropped in late spring to expose mud flats. The moist soilplants grow rapidly in these nutrient-rich sediments. By fall,the moist soil plants have flowered and produced seeds.Flooding the marsh allows the ducks to swim among themoist soil plants and feed. The preferred water depth forfeeding dabbling ducks and geese is 6 to 12 inches.


Another common method aimed at increasing food for water-fowl is flooding grain fields or oak forests. Again, the key isthe ability to control water levels. If grain fields are flooded in the summer, the grain crop won’t mature. After the crophas ripened, it’s slowly flooded, providing the waterfowl withaccess to the grains.

This technique is extremely effective for providing food formost dabbling ducks and geese. Flooding oak forests in thefall and winter is mostly used to provide acorns and otherforest seeds for feeding wood ducks and mallards. The treescan be flooded for only a few months in the fall and winter.Otherwise they’ll be killed. Also, the ideal water depth is lessthan 12 inches. This technique is extremely effective in thesoutheast United States and around the lower MississippiRiver.

FIGURE 26—Marsh smartweed is a valuable foodplant for waterfowl.

FIGURE 27—The seeds of wild millet are attractiveto feeding waterfowl. (Courtesy OklahomaDepartment of Wildlife Conservation)


Creating refuge areas. During hunting seasons, waterfowlneed undisturbed places to rest (or loaf). This is accomplishedby creating refuge areas where hunting isn’t allowed. Therefuge area should meet all the habitat needs of waterfowl.

One special type of habitat is the loafing habitat. Somewaterfowl prefer to loaf in large bodies of water where theyhave good visibility and feel secure from predators. Manysimply float on the water, but then they have to swim to keepthe wind from blowing them across the water. If available,they prefer to sit on floating logs so that they don’t have toswim against the wind. By anchoring logs in marshes, loaf-ing sites can be created. The logs shouldn’t be placed inareas where they’ll interfere with other operations, such asnear boat ramps.

Brood cover. Another special habitat needed by most ducksis brood cover. This is a place where the young ducks aresecure from predators. Good brood cover is thick vegetationover the water that provides a canopy where ducks are hid-den from hawks and other avian predators. This cover canbe shrubs—like buttonbush or willows—or emergent wetlandplants—like cattails or arrowhead. Ideal brood cover wouldalso provide food for the young.

Who Manages a Habitat?Most waterfowl habitat in the United States is privatelyowned, typically by farmers and ranchers. Unfortunately,most farmers and ranchers don’t engage in any managementactions that are directed primarily at waterfowl. Still, manyof their actions do benefit waterfowl.

Growing grain crops provides food for waterfowl. Maintainingpastures and hayfields provides nesting habitats for them.And creating livestock water holes provides wetland areas for waterfowl. Some farmers and ranchers do manage theirland specifically for waterfowl. Their motivation may be per-sonal interests, or it may be because they rent or lease theirproperty to hunters.

The federal government influences practices on farms andother private lands through various regulations and pro-grams. Provisions in the Clean Water Act prohibit wetland


drainage or filling. The Farm Bills of 1990 and 1995 pro-vided cash payment to many farmers who agreed to leavecertain areas in grassy cover. This is known as theConservation Reserve Program. Over the years, theConservation Reserve Program and other similar programshave provided millions of acres of excellent habitat forupland nesting ducks.

Across the nation, many private areas are managed specifi-cally for waterfowl. Typically, these areas are hunting clubsthat charge an annual membership fee. Management ofthese areas varies widely. Some clubs merely provide lodgingfor members, whereas others manage the habitat intensivelyfor waterfowl and employ a professional biologist and staff.

Various organizations other than hunt clubs own and man-age property for waterfowl. Some organizations have a localfocus, whereas others have a broad national interest. Theseorganizations are generally nonprofit and are supported bymembership fees and grants. Some organizations acquireproperty and then give it to government agencies to manage.The most well-known, nongovernment wetland and waterfowlconservation organization that focuses on waterfowl is DucksUnlimited (national headquarters, Memphis, Tennessee: 1-800-45DUCKS).

Federal government lands. The government—at all levels—owns and manages property for waterfowl. The U.S. Fish andWildlife Service manages more waterfowl habitat than anyother agency. It owns more than 92 million acres distributedamong more than 500 wildlife refuges and 26,000 waterfowlproduction areas.

U.S. Fish and Wildlife refuges are typically rather large,cover several thousand acres (usually about 5000), and aremanaged primarily for waterfowl. Waterfowl production areastend to be smaller—usually less than 500 acres. These areasare located in the North Central United States and are man-aged for nesting waterfowl.

Waterfowl production areas are entirely open to publichunting and fishing, whereas wildlife refuges may be only partially open to hunting or fishing. Money for operating theU.S. Fish and Wildlife Service comes from the federal govern-ment’s general fund and a few special funds.


Duck stamps. One fund is generated by the sale of annualmigratory bird conservation stamps. These stamps are morecommonly known as “duck stamps.” Anyone over the age of16 years must purchase these stamps to hunt ducks or otherwaterfowl (Figure 28). Money from the sale of duck stamps isused to purchase wildlife refuges and waterfowl productionareas. Other branches of the federal government—includingthe National Park Service, Forest Service, Bureau of LandManagement, and all branches of the military—managewaterfowl to some extent on their properties.

State lands. Each state owns wildlife areas. Many are man-aged intensively for waterfowl. On others, waterfowl may beof minor importance. Hunting is allowed on at least portionsof most state areas, because hunting license fees and taxeson guns and ammunition fund the land acquisition.

In addition, most states also sell state waterfowl stamps.They’re similar to the federal duck stamp in that waterfowlhunters must purchase one to hunt waterfowl within thestate. Revenue from the sale of state duck stamps is typicallyused to fund waterfowl habitat acquisition and management.

Other lands. Some counties, cities, and towns own proper-ties that are managed as parks or natural areas that providebenefits to waterfowl. Many schools and colleges also ownand manage natural areas for waterfowl.

FIGURE 28—The federalduck stamp, whichchanges every year, isrequired for all waterfowlhunters. (Courtesy FederalDuck Stamp Program)


Self-Check 41. Define the term carrying capacity.

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2. What is the ideal water depth for most dabbling ducks and geese to feed in?

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3. Name five ways to increase the nesting success of mallards.

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MANAGEMENT OF POPULATIONSTHROUGH HARVESTA population was defined earlier as a group of organisms ofthe same species in a given geographic area. Although thisdefinition seems rather straightforward, waterfowl managersoccasionally find that some birds don’t clearly fit into definedpopulation units. Some of the confusion stems from the factthat birds are mobile and don’t stay within a predefined geographic area.

For example, a male mallard may follow its mate to nest inMichigan in one year and then follow a new mate to a nest-ing site in North Dakota in the next year. Thus, it would be unclear if the male belonged to the population of mallardsthat nested in Michigan or those that nested in North Dakota.

Not only do some waterfowl nest in different areas from oneyear to the next, but they also may spend the winter in differ-ent areas. For example, a pintail may spend its first winter inCalifornia and then its next winter in Texas. To help identifypopulation units and understand movements of individuals,managers mark waterfowl with a variety of devices.

The Science of Population ManagementManagers have established population objectives for manypopulation units. The objectives are usually numeric goalsthat can be readily measured. Objectives should clearlyspecify the time of year, species, and area that’s referenced.

For example, the population objective for the Atlantic popu-lation of Canada geese is 180,000 breeding pairs. For manyNorth American duck populations, the average number thatwere present in the 1970s is used as a population objective.For mallards, this is 8.1 million in the spring. The popula-tion objectives for North American ducks were established ina report jointly prepared by the Mexican, Canadian, and U.S.governments. This report is the North American WaterfowlManagement Plan.

By themselves, population objectives are of little value.Waterfowl managers must periodically monitor the popula-tions to determine if they’re above, below, or at objective


levels. Most monitoring efforts are done on an annual basis.The monitoring is completed at times that allow assessmentof the objective. For example, if an objective for a populationunit relates to the size of the population in the spring, themonitoring must be completed during the spring rather thanduring the fall or winter.

Hunting is one tool for managing population size. When thecurrent population size is below the population objective,managers want the population to increase. To do this, theywill often restrict the length of the hunting season and make bag limits smaller. They hope to reduce the size of the harvest and thus the total death rate.

If the total death rate declines below the birth rate, then thepopulation increases, assuming that immigration equalsemigration. If the population is above the population objec-tive, managers then lengthen the hunting season andincrease bag limits. They hope to increase the harvest andthus the death rate so that the population declines to theobjective level. The optimal harvest is usually considered tobe the amount of harvest that would result in the populationreaching the objective level.

It’s difficult for managers to precisely control the size ofwaterfowl populations by manipulating hunting seasons.This is because of the natural variations between the birthand death rates of waterfowl from year to year. The variationmakes it difficult to predict exactly what the birth rates anddeath rates will be in any year. Even if harvest were heldconstant from year to year, waterfowl populations would naturally fluctuate. In years with high birth rates and lowdeath rates, the population would increase. In other years,the reverse might be true, and populations would decline.

Another reason that managers have difficulty controlling thesize of waterfowl populations is because of variations in theharvests that occurs with hunting seasons. Harvests varyaccording to how many hunters participate, how many timeseach hunts, how skillful they are, how vulnerable the birdsare to hunting, and other factors. All of these factors varyfrom year to year.

Normally, managers can control the elements of the huntingseason (season opening day and closing day, bag limits,


shooting hours). But managers can’t control the harvest.However, in some cases, the harvest is more directly con-trolled. For example, the harvest of Canada geese in somestates is monitored daily. The hunting season is then stoppedif the total harvest exceeds the optimal harvest level.

Administration of Hunting SeasonsHunting seasons for waterfowl in the United States areadministered jointly by the federal and state governments.The Migratory Bird Treaty Act of 1918 and other supplementaltreaties that the United States has with Canada and Mexicodictate which migratory species are eligible for hunting. Thetreaty specifies that migratory bird hunting seasons in theUnited States are closed, unless specifically opened each year.Further, the treaty states that in the United States, theDepartment of the Interior has the ultimate responsibility toensure that wildlife populations are maintained.

Many of the waterfowl hunting regulations don’t change from year to year or among areas. These are called basic regulations. Some of the many basic regulations are restric-tions on the size of shotguns and shot size that can be used.Also, there are prohibitions against using bait such as cornor tame birds to attract wild waterfowl.

More specific regulations, such as daily bag limits or seasonlengths, change as often as every year and are called annualregulations. These regulations are determined jointly by the state and federal government through an elaborate con-sultation process that also includes Canadian and Mexicangovernments and the public. Staff members from each state’swildlife agency represent the states. Staff members from theU.S. Department of the Interior and U.S. Fish and WildlifeService represent the federal government.

Specific annual regulations, like earliest possible openingdates, latest possible closing dates, season lengths, and baglimits, are developed each year for all migratory species.

The first step is for state wildlife agency staff members tomeet at flyway meetings. North America is divided into fouradministrative flyways: Atlantic, Mississippi, Central, and

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Pacific (Figure 29). Each flyway is a group of states andprovinces that are adjacent to one another. Generally, thesame population of waterfowl uses each flyway.

Because most migrations occur in a north-south direction,the flyways are physically oriented in this direction (e.g.,both New York and Florida are in the Atlantic flyway). Statesand provinces in the same flyway generally share the samewaterfowl populations and often similar concerns regardingwaterfowl management.

Much of the management of waterfowl harvest is done at the flyway level. For example, duck season lengths and baglimits are usually the same within a flyway but often differamong flyways.

Within each flyway meeting, current information on populations and expected birth rates are considered.Recommendations from each flyway meeting determine the upcoming year’s regulations. The recommendationsaren’t always the same from one flyway to the next.

The U.S. Fish and Wildlife Service committee members thenconsider the flyways recommendations and formulate theirown proposals for hunting regulations. These proposals are publicized. Then the public, including any organization

FIGURE 29—Map of the Four U.S. Flyways(Courtesy U.S. Fish andWildlife Service)


representatives—can comment on the proposals. Afterconsidering the public comments, the Department of theInterior finalizes the current year’s regulations just beforethe fall hunting seasons can begin.

The regulations that are finalized by the Department of theInterior are actually only frameworks in which the statesmust comply. The frameworks specify the outside limits forhunting regulations.

For example, the framework might be that a state’s duckhunting season is no more than 50 days long and mustoccur between October 1 and January 20. Given that frame-work, states then select the specific season dates for theirown state. Thus, Wisconsin might select a season of October1 to November 19, whereas Arkansas might select a seasonof December 2 to January 20. Both seasons would be incompliance with the framework of regulations.

Public participation. Because wildlife is a resource ownedby the public, there are numerous opportunities for thepublic to comment on proposed hunting regulations. In theannual federal process, there are two periods when publiccomment is invited: when frameworks are proposed, andwhen states are making their season selections. Most statesalso hold annual public hearings during which seasonproposals are presented and public comments are invited.In addition, a private citizen can always write to the director of his or her state fish and wildlife agency or the Director ofthe U.S. Fish and Wildlife Service to comment on proposedregulations or issues.

Law enforcement is key to having effective hunting regula-tions. The U.S. Fish and Wildlife Service has a staff of lawenforcement agents, with one or more field agents in eachstate. States maintain a much larger force of conservationofficers. Many states have one officer per county. Mostconservation officers have authority to enforce both stateand federal wildlife regulations. In some areas, local andstate police officers also enforce wildlife regulations.


Self-Check 51. Define the term population objective.

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2. What are the four administrative flyways in the United States?

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3. Name two instances for which comments on waterfowl regulations are invited from the public.

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MONITORING WATERFOWLPOPULATIONS

Population SizeCensus. There are many ways to estimate the size of water-fowl populations in specific areas. In some situations it’spossible to directly count each individual from the ground,boats, or airplanes. This technique of population estimationis called census. A census works best for small areas whenwaterfowl are concentrated in open areas and are easily seen.Waterfowl censuses are often conducted at specific refuges inwinter months, when ducks and geese flock together on largelakes or in fields. Even in a census, biologists at times mustdo their best job to estimate the numbers of birds in largeflocks.

Truthing. Sometimes it may be necessary to verify that fieldestimates are reasonably accurate. This process is known as truthing. One method of truthing uses aerial photographs.Biologists take photographs of flocks that they’ve just sur-veyed and then compare their field estimates with moreexact counts from the photographs. They don’t photographevery flock—only a sample.

If enough truthing is conducted, biologists can determine ifthey tend to underestimate or overestimate the size of flocksin their field counts. Truthing is also used to develop a correc-tion factor to improve the accuracy of the field estimates.

Aerial counts and photos. This technique has been usedto estimate the size of the snow goose population in the St.Lawrence River Valley of New York and Quebec in spring. In a hypothetical example, a biologist estimates the size of three flocks of snow geese at 5700, 11,000, and 17,300 (a total of 34,000). The biologist also takes aerial photographsof these same three flocks. The biologist then estimates atotal of 200,000 other geese in 10 more flocks. However, thebiologist takes no photos of these last 10 flocks. The overallestimate from field counts is thus 234,000.


Later, the biologist carefully examines the photographs of thethree flocks and determines that the number in each flockwas actually 7128, 14,220, and 24,552—a total of 45,900. So,in these three flocks, the true number of waterfowl was 1.35times larger than that which was estimated in the field. Thisis the correction factor.

The correction factor is calculated by dividing the true countby the field estimate (45,900 ÷ 34,000 = 1.35). Multiplyingthe correction factor by the total field estimates yields thecorrect estimate. In this case, 1.35 × 234,000 = 315,900.Thus, the best estimate was that 315,900 snow geese werepresent in the three flocks. In real cases, field estimatesoften tend to be lower than true counts.

Sample survey. When managers need to know the totalsize of a waterfowl population, it’s usually not practical to do a complete census. This is because populations are oftenspread over large areas. In these situations, counts areconducted from only a sample of the entire area. This methodis called a sample survey.

Two of the most commonly used sampling techniques aretransect surveys and plot surveys. For transect surveys, thesample counts are obtained along strips, often from an airplane. In plot surveys, the sample counts are taken fromsquare or rectangular areas. They may be obtained by peopleon the ground or in boats or helicopters.

Transect survey. One of the best wildlife surveys in theworld is a transect survey of waterfowl in North America. Thesurvey has been conducted each spring since 1955 in muchof Canada and the northern United States (Figure 30). Allwaterfowl seen within one-quarter-mile-wide strips—ortransects—are counted. The transects total about 75,000miles long and are flown by 12 crews. The total sample areais divided into about 59 smaller areas—called strata—foranalytic purposes (Figure 31).


Each crew has a pilot and an observer. The plane flies 100 to 150 feet above the ground at a speed of about 100 milesper hour. The pilot records the number of each species ofwaterfowl that’s seen within one-eighth mile of his or herside of the airplane. The observer records the same informa-tion within one-eighth mile of his or her side of the airplane.Data are recorded into small tape recorders or computersthat are carried on the plane.

A complicated truthing process involving surveys from theground is used to correct the aerial counts. Quick and accurate identification and counting of waterfowl from anairplane requires great skill and practice. The pilot also hasthe additional task of flying and navigating the airplane.Overall, it’s a demanding job.

Here’s an example of a transect survey. Suppose that wewish to estimate the number of Canada geese present in asquare area that’s 100 miles long and 100 miles wide. Thus,this area covers 10,000 square miles (100 miles long × 100miles wide = 10,000 square miles). In this area, 8 transectsare flown. Each transect is 100 miles long and one quartermile wide. Thus, the total area sampled is 200 square miles(8 transects × 100 miles long × 0.25 miles wide = 200 squaremiles).

FIGURE 30—Duck Survey Crew (Courtesy of David Caithamer/U.S. Fish and Wildlife Service Photo)


FIGURE 31—Transect survey areas are used to determine sizes of spring waterfowl populations in North America.


Suppose, too, that we count a total of 720 geese in ourtransects. The number of geese counted on our sample areamust be multiplied by an expansion factor to estimate thetotal number of geese present in the entire area. The expan-sion factor is determined by dividing the total area by thesample area. In our example the expansion factor is 50(10,000 ÷ 200 = 50).

Our overall estimate for geese in the entire area is the productof 720 (number of geese observed in the sample) multipliedby 50 (the expansion factor). The estimate is 36,000 geese inthe entire area. Estimating the number of waterfowl from aplot survey is done in a similar manner.

HarvestHarvest of each species of waterfowl in the United States isestimated annually through a two-part survey. In the firstpart, a random selection of duck stamp purchasers are sentquestionnaires. They’re asked if they’ve hunted waterfowl; if so, they’re asked to specify how many ducks and geesethey’ve harvested. The second part of the survey (see theHarvest information program discussed below) involves a sample of duck wings and goose tails that are submitted by cooperating hunters.

Duck stamp questionnaire. From the questionnaires justdescribed, about 5% of the people who buy duck stampssaid that they didn’t hunt waterfowl. From those who indi-cated that they did hunt, the average number of ducks andgeese harvested per hunter is calculated.

Because the number of duck stamps sold is monitored, it’spossible to estimate the total harvest of ducks and geese.This is done by multiplying the average number killed perhunter by the number of stamps sold to hunters. For exam-ple, in 1998 there were about 1,525,000 adult waterfowlhunters in the United States. Each harvested, on average,10.4 ducks and 2.0 geese for the entire season. Expandingthese averages by the number of adult waterfowl huntersyields harvest estimates of 15,860,000 ducks (1,525,000hunters × 10.4 ducks per hunter) and 3,050,000 geese(1,525,000 hunters × 2.0 geese per hunter).


Harvest information program. In all states, a harvestinformation program was initiated in 1998 or earlier. Thissystem requires all migratory bird hunters—regardless ofage—to have a permit to hunt waterfowl or other migratorybirds. These hunters are questioned to determine their har-vest of waterfowl. Preliminary analysis shows that estimatesfrom the harvest information program are better than thosefrom the survey of duck stamp purchasers. Eventually, datafrom the harvest information program will replace dataobtained from questionnaires sent to duck stamp purchasers.

By examining the sample of wings from harvested ducks andtails from harvested geese, managers can determine the totalnumber of each species harvested and the proportion thatwere adults, young, males, and females. Complete,unplucked wings are taken from ducks to identify species,age, and sex. Complete, unplucked tails are taken from geeseto identify species and age. (Goose gender can’t be deter-mined from the tail.) Hunters cooperating in this survey aregiven envelopes with prepaid postage and asked to send onewing from each duck and the tail from each goose that theyharvest. Then the waterfowl parts are sent to freezer storagefacilities in each flyway.

After the season, biologists gather to examine wings andtails. From the wing of a duck, the species, age, and sex canbe determined. From the tail of a goose, its species and agecan be determined. The data are summarized and the com-position of duck and goose harvest is estimated. Forexample, in 1998, about 100,000 duck wings were received.About 33% were from mallards. Of the mallard wings, 47%were from young and 53% were from adults. Males composedabout 69% of the harvest. The species and age compositionof the goose harvest was determined from about 15,000goose tails examined in 1998.

Tracking WaterfowlMarking. Waterfowl managers often mark and release individual birds to

• Understand how members of a population move

• Help identify population units


To mark the birds, the managers must first capture themwithout harm.

Corralling. One capture method is to corral or round upbirds when they’re flightless. Typically, this is done in mid-summer—when the young are still too small to fly, and theadults are molting their wing feathers. This technique iscommonly used with geese, but it can also work with ducksand swans.

Typically, a holding pen with one open side is erected on theshore of a lake where the flightless birds are concentrated. A crew of people who are in boats, on foot, or even in heli-copters then herd the waterfowl into the pen. Once the birdsare in the pen, the door is closed so that no individuals canescape.

Traps. Waterfowl can also be captured in baited traps.Various designs have been developed, but most have similarcharacteristics. Typically, they’re constructed of wire fencingand placed in shallow water where birds have been feeding(Figure 32). The opening is funnel-shaped so that the birdscan easily enter the trap but can’t escape. Another door isused to remove the birds.

The traps—especially the funnel openings—are baited withgrain that attracts feeding birds. Trap tops are often con-structed of soft netting so that flying birds aren’t injured.The traps are checked once or twice each day.

FIGURE 32—Grain is used tobait the funnel opening of aduck trap. (Courtesy U.S.Fish and Wildlife Service)


Rocket nets. A third method of capturing waterfowl is withrocket nets. A large net—often more than 50 feet long—isattached to several small rockets. The rockets are situated to pull the net over a clear area where waterfowl are encour-aged—with baiting—to concentrate. Usually, the net is set up on a beach area or in a field. The rockets are activatedremotely by electric wires.

Rocket netting can be very dangerous. The rockets areextremely powerful and can easily kill a person if he or she is in the line of fire. Another risk is that the flames from therockets can cause ground vegetation to catch fire. Care mustbe taken to reduce death or injury to captured birds. The netsshould never be used over water, because the birds easilybecome entangled and may drown. Also, the flying net caneasily decapitate or injure waterfowl. Despite all their poten-tial problems, when rocket nets are used properly they can bevery effective for capturing large numbers of waterfowl quickly.

Follow-up leg banding data. Once captured, most water-fowl are marked with a metal leg band. A federal permit forbird banding is required from the Bird Banding Laboratoryof the U.S. Department of the Interior. Each band has aunique number that can be traced to an individual bird.

Various data are recorded for each bird. This includes thespecies, age, and sex of the bird and the exact date andplace of marking. Recovery of bands usually occurs byhunters. However, some recovery also occurs when birds are recaptured or found dead during disease outbreaks. Leg banding has been an effective source of data for speciesthat are easily captured and frequently shot by hunters.

Whenever a banded bird is found, its band number shouldbe reported to the Bird Banding Laboratory. The laboratorywill also need to know the place and date that the band wasrecovered and how it was recovered—for example, if the birdwas shot. The Bird Banding Laboratory maintains a data-base of all bandings and band recoveries that have occurredin North America. Band recoveries can be reported by mail(12100 Beach Forest Road, Laurel, Maryland 20708-4037) or phone (1-800-327-2263). Those individuals reporting aband recovery receive information on the banded bird and acertificate from the banding laboratory.


Limitations of leg banding. Leg banding may be inade-quate for some studies of waterfowl. One of the biggestlimitations of leg banding is that most banded birds arenever recovered by anyone. Often, less than 2% of the bandsare recovered even once. This usually occurs when the birdis shot. Even fewer banded birds are recaptured by biolo-gists. For many species—like sea ducks nesting in remoteareas who are rarely shot by hunters—leg banding has pro-vided very little information. In these cases, managers mustrely on other, more costly techniques. One of these methodsis marking with radiotransmitters. State and federal permitsare also required for performing this procedure.

Radiotransmitters. These units emit a radio signal thatcan be detected by special receivers. The biggest advantageof using radiotransmitters is that data about individuals canbe gathered almost continuously. The disadvantages of usingradiotransmitters are

• Their high cost

• The possibility of mortality. Some birds may die from thestress of being outfitted with a radiotransmitter if itsload is too heavy or if a backpack is incorrectly placed. Most radiotransmitters are powered by a battery exclu-sively. But some units also use solar power. Small andlight radiotransmitters can be used for all waterfowl.However, larger birds can tolerate slightly heavier radio-transmitters. To minimize negative impact from theweight of the radiotransmitter, it shouldn’t exceed 3% ofthe bird’s body weight. Radiotransmitters have beenattached to waterfowl using various methods. Theseinclude

• Backpack style

• Neck collars

• Surgically sewn or glued to the skin

• Implanted surgically


The range of most radiotransmitters is usually between 2and 50 miles. Receivers in vehicles, including airplanes,monitor the radiotransmitters. Some radiotransmitter signalsare automatically received with satellites, which means thatno special fieldwork is needed to monitor the movement ofthe birds. This has proved to be especially useful in trackinglong-distance movements of waterfowl, such as duringmigration.


INTERNET JOURNAL AND REFLECTION ACTIVITY

Throughout the Wildlife Conservation and Forestry program, you’ll be invited to expand your knowledge of this field through an Internet expedi-tion. Get a separate notebook in which you can record your thoughts andobservations However, do not send your journal entries to the school.

If you have access to the Internet, you might enjoy an Internet expedition in thefield of wildlife conservation/forestry. The U.S. Fish and Wildlife Service has animage library at http://images.fws.gov/. Start there and select a keyword, forexample, Canada Geese. View the image(s) for that keyword and follow up onone or two topics that interest you the most. Do an Internet search using termsassociated with the image(s) and topic(s). Summarize the results of your searchin the notebook.

Think about the results of your Internet search. What do they mean to you?What further study or fieldwork would you like to do as a result of this increasedknowledge?


Self-Check 61. What are the two surveys used to estimate the number of mallards harvested in the

United States each year?

__________________________________________________________________________

__________________________________________________________________________

2. When is it most appropriate to conduct a census of waterfowl populations?

__________________________________________________________________________

3. When is a sample survey more appropriate than a census?

__________________________________________________________________________

4. What should someone do upon finding or shooting a banded bird?

__________________________________________________________________________


77

Self-Check 11. All of the following:

• Front three toes webbed

• Blunt and flattened bills with lamellae

• Tongues serrated on edges

• Elongated necks

• Thick insulating feathers and well-developed oil glands

• Eggs white or pale and without spots

• Incubation delayed until the last egg is laid

• Precocial young

• Annual flightless period for adults

2. Precocial means that the young are hatched with downfeathers covering their body, open eyes, and sufficientcoordination to walk, swim, and feed.

3. There are 47 species that nest in North America.

4. Any four of the following:

• Whether the sexes appear similar

• The age they first breed

• Amount of color in the male’s plumage

• The relative leg position on the body

• The scale pattern on the leg

• Presence of a lobed hind toe

Answers

Answers

Self-Check Answers78

Self-Check 21. The male mallard, or drake, has an iridescent green

head, chestnut chest, gray sides, black rump, and olive-green bill.

2. Brooding is a behavior by which the hen covers theyoung with her wings and her body to help them staywarm and dry.

3. Young ducks are called ducklings; young geese arecalled goslings; and young swans are called cygnets.

4. Any of the geese or swans

5. The wood duck

Self-Check 31. The pair mate on the water, with the male climbing up

onto the back of the female and grasping her on theneck with his bill. He then briefly inserts his penis andtransfers his sperm into the female’s cloaca.

2. • When waterfowl are very young and growing rapidly

• When waterfowl are growing new feathers during molts

• When female waterfowl are growing eggs in their reproductive tract

3. Natal plumage, juvenile plumage, basic plumage, andalternate or breeding plumage

4. Hormone levels in their bodies react to changes inlength of daylight and trigger the urge to migrate.

5. • The tail feathers have notched tips in the young and pointed tips in adults.

• The penis is small in the young and large in adults.

• Characteristics of the wing feathers are different among ages.

6. Lead poisoning

Self-Check Answers 79

Self-Check 41. The size of the population that a habitat can sustain is

called its carrying capacity.

2. Most dabbling ducks and geese prefer to feed in areasflooded with 6 to 12 inches of water.

3. Any five of the following:

• Plant and maintain native prairie grasses in upland nesting areas.

• Periodically mow or burn existing upland cover to keep it vigorous and not too dense.

• Construct nesting islands in marshes.

• Place floating nesting platforms in marshes.

• Erect nesting cones in marshes.

• Trap or poison predators.

• Eliminate predator den sites, like old building foundations and rock piles.

Self-Check 51. Population objectives are usually numeric goals that can

be readily measured. Objectives should clearly specifythe time of year, species, and area that is referenced.

2. The four administrative flyways are the Atlantic,Mississippi, Central, and Pacific.

3. In the annual federal process, there are two periodswhen public comment is invited: when frameworks areproposed and when states are making their seasonselections. Most states also hold annual public hearings,where season proposals are presented and public comments are invited.

Self-Check 61. A random selection of duck stamp purchasers are sent

questionnaires. They’re asked if they’ve hunted water-fowl. If so, they’re asked to specify how many ducks andgeese they’ve harvested. The second survey involves asample of duck wings and goose tails that are submittedby cooperating hunters.

2. A census works best for small areas when waterfowl areconcentrated in open areas and are easily seen, whichusually occurs in winter months.

3. When one needs to know the total size of a waterfowlpopulation—and the population is often spread over alarge area—it’s best to conduct a sample survey.

4. Whenever a banded bird is found or shot, its band num-ber should be reported to the Bird Banding Laboratoryof the U.S. Department of the Interior.

Self-Check Answers80

81


Log in as a student at http://www.pennfoster.edu, go to your

student portal, and click on Take Exam next to the lesson you’re

working on. Take your exam, and get your grades moments

after you finish. If you pass, you’ll be given the correct answers

with page references. If you fail, you’ll be given retest instruc-

tions.

Questions 1–20: Select the one best answer to each question.

1. Which statement is correct?

A. Mallards don’t have a basic plumage.B. Mallards don’t have an alternate plumage.C. Canada geese don’t have a basic plumage.D. Canada geese don’t have an alternate plumage.

2. Which sequence of events is in the correct order?

A. Egg laying, molting of wing feathers, hatching of eggsB. Pairing, egg laying, molting of wing feathersC. Hatching of eggs, migration to wintering areas, molting of

wing feathersD. Spring migration, molting of wing feathers, egg laying

3. Which of the methods for capturing waterfowl is the most dan-gerous?

A. Capturing them in a nest boxB. Trapping them in a baited funnel trapC. Corralling or rounding them up when they’re flightlessD. Rocket-netting them over bait

EXAMINATION NUMBER:

02200600

To take your exam, go to http://www.pennfoster.edu

Examination

Examination

Examination82

4. In a field survey, the size of 2 flocks of swans was estimated to consist of 3000 and 5000individuals. Photos reveal that there actually were 3500 and 8500 swans in these flocks. In5 other flocks, there were an estimated 20,000 swans. What is the most accurate estimateof the total number of swans in the 7 flocks?

A. 28,000 C. 42,000B. 32,000 D. 70,000

5. You’ve discovered the fossils of an extinct waterfowl species. It was about the size of aturkey, with forward-positioned legs having reticulated scales and mouth and throat havingevidence of plant remains. Based on these characteristics, which tribe would the descrip-tion best fit?

A. Cairini—perching ducks C. Dendrocygnini—whistling ducksB. Aythyini—bay ducks D. Anserini—geese and swans

6. Which goose is using the most energy? Assume that the goose is the same size in eachcase.

A. One who is sleeping in an area where the temperature is 45°FB. One who is feeding in an area where the temperature is 45°FC. One who is sleeping in an area where the temperature is 30°FD. One who is flying in an area where the temperature is 45°F

7. A marsh has sufficient food to sustain no more than 50 adult mallards and 250 mallardducklings. There’s no brood cover, and any ducklings on the marsh are soon killed by pred-ators. Adult mallards on the marsh are never killed by predators. Which of the following iscorrect about this marsh?

A. Its carrying capacity is 50 mallards.B. Its carrying capacity is 300 mallards.C. Its limiting factor for adult mallards is cover from predators.D. Its carrying capacity can be increased by erecting nesting cones.

8. Who is required by law to have a federal duck stamp?

A. Anyone in the United States—regardless of age—who hunts any migratory birdsB. Anyone in the United States—regardless of age—who hunts waterfowlC. Anyone in the United States—16 years or older—who hunts any migratory birdsD. Anyone in the United States—16 years or older—who hunts waterfowl

9. Which of the following descriptions is true of bay ducks?

A. The males are brightly colored.B. The legs are located far back on the body, and the birds don’t swim well.C. The legs are located far back on the body, and some birds have to run across the

water to become airborne.D. Their wings are very well developed.

Examination 83

10. The daily bag limit for lesser scaup was six during 1996, 1997, and 1998. In 1999 the limitwas reduced to three. Waterfowl managers probably did this because

A. the optimal harvest was being achieved in most years during 1996 to 1998.B. the actual harvest was below the optimal harvest in most years during 1996 to 1998.C. the actual harvest was above the optimal harvest in most years during 1996 to 1998.D. the population objective was lowered in 1999.

11. Large numbers of waterfowl are found dead on a shallow lake in midsummer. Some livebirds have trouble holding their head out of the water. What should you suspect is causingthe mortality here?

A. Botulism C. Avian choleraB. Hypothermia D. Lead poisoning

12. Which of the following is correct?

A. Adult male ruddy ducks don’t have blue bills in spring.B. Neither sex of Canada geese have black bills.C. Lesser scaup are difficult to distinguish from greater scaup.D. Cygnets aren’t gray.

13. What agency owns and operates more than 500 wildlife refuges and 26,000 waterfowl production areas?

A. The Bureau of Land Management C. Ducks UnlimitedB. The U.S. Fish and Wildlife Service D. The National Park Service

14. An island that’s 20,160 square miles has a population of snow geese. Managers design atransect survey to determine the size of this population. They fly 12 transects and count atotal of 480 snow geese. Each transect is 0.25 mile wide and 32 miles long. What is the estimated size of the snow goose population on the entire island? Assume that allsnow geese present in these transects were counted.

A. 46,080 C. 100,800B. 50,400 D. 1,209,600

15. Which would lead to an increasing population?

A. Death rate equals birth rate, and immigration equals emigration.B. Death rate is greater than birth rate, and immigration equals emigration.C. Death rate is greater than birth rate, and immigration is less than emigration.D. Death rate is lower than birth rate, and immigration equals emigration.

Examination84

16. When comparing mallards with Canada geese, which of the following is correct?

A. Both species are monogamous.B. The clutch size of mallards is usually smaller than the clutch size of Canada geese.C. The sexes appear similar in mallards, but different in Canada geese.D. Neither mallards nor Canada geese eat seeds and vegetation.

17. The Migratory Bird Treaty Act and other supplemental treaties

A. dictate that hunting seasons on waterfowl are closed unless specifically opened.B. dictate that states have ultimate responsibility to ensure maintenance of waterfowl

populations.C. dictate that waterfowl seasons must be in accordance with desires of the states.D. don’t specify which waterfowl species are eligible for hunting seasons.

18. Waterfowl managers sometimes attempt to control the numbers of animals preying onduck nests. Regarding the control of predators, which is correct?

A. Predators may be controlled with poisoned chicken eggs.B. Benefits of trapping predators normally are long lasting.C. Burying rock piles helps to increase the number of mammalian predators in an area.D. Pets cannot be killed in predator control operations.

19. Which of the following is true of redheads and ruddy ducks?

A. They lay their eggs in tree cavities or boxes.B. They form lifelong pair bonds.C. They care for their young for more than one year.D. They lay their eggs in the nests of other ducks.

20. Which of the following is a basic regulation?

A. Daily bag limit of geeseB. Opening day of the duck seasonC. Prohibition against using live ducks as decoy birdsD. Length of the duck season

Documents

Study Unit Wildlife Management: Waterfowllessons.pennfoster.com/pdf/022006.pdf · 2017-11-30 · The necks of most waterfowl are long. This allows them to reach down through the water