Bucephala albeolabufflehead

Last updated:

Geographic Range

Buffleheads are native to North America. Their summer breeding range includes central Alaska and extends south to British Columbia and east to Saskatchewan. Isolated breeding populations can also be found throughout the northern United States and in Quebec. Their winter distribution is generally split into two populations, one on the east coast and the other on the west coast of North America. The east coast population is usually found from New Jersey to North Carolina, and can be reaches up to the Bay of Fundy in New Brunswick, Canada. The west coast population is concentrated in British Columbia, Washington, and California. The most substantial winter confluence occurs on British Columbia’s Vancouver Island and the Californian coast. They are less likely to be found moving inland from the western Klamath Basin in California and Oregon toward the Mississippi River. (Gauthier, 1993; Usai, 1999)

Habitat

Buffleheads live in boreal forests and aspen parklands as well as seasonally-flooded wetlands and estuaries. They can be found along ecotones, and in marshes, farmlands, grasslands, and open waters. They prefer ponds and small lakes with no drainage while breeding. During migration, they use rivers and available water bodies as temporary habitat. Their winter habitat includes salty bodies of water like marshes, coastlines, and estuaries with shelter. They are not found at high mountain elevations. (Gammonley and Heitmeyer, 1990; Gauthier, 1993; Knutsen and King, 2004; McKinney, 2004)

Physical Description

Buffleheads are small diving ducks that exhibit strong sexual dimorphism. Males with breeding plumage are predominately black and white, with a black head and back that appears iridescent green and purple. They have a white underbelly and a distinguishing large white patch extending from the nape of the neck to the crown of the head. Males have blue-gray bills and pink webbed feet. Females are similar in plumage to male yearlings. They are grey on the bottom and brown on top with a white patch on the sides of the head. Both male yearlings and adult females have bills that are dark gray to black and legs and toes that are dark pink while webbed feet are brown. The ear patch of female buffleheads is more defined than the that of yearling males. The downy coats of hatchlings are black to dark grey with a white patched cheeks, throats, lower breasts, and bellies. (Gauthier, 1993; McKinney and McWilliams, 2005; Usai, 1999)

Buffleheads weigh 270 to 513 grams and are 32 to 40 cm long. Their wingspan is 16.9 to 17.5 cm long. Sexual dimorphism is exhibited in their size as well. Adult males weigh 450 grams on average and are 35 to 40 cm long, while females weigh 325 grams on average and are 32 to 35 cm long. Their folded wings are 18 cm or less in adults and their tails are less than 8 cm long. (Gauthier, 1993)

Adult males are sometimes mistaken for common goldeneyes (Bucephala clangula), Barrow’s goldeneyes (<< Bucephala islandica>>) and hooded mergansers (Lophodytes cucullatus). Unlike buffleheads, goldeneyes have a white patch that starts below the eye and extends towards the beak and they both have golden eyes. Hooded mergansers are larger and have a fan-shaped white patch on their heads. Unlike bufflehead males, their chests and wings haave white stripes and a brownish or golden brown underside. (Dugger, et al., 2009; Eadie, et al., 1995)

  • Sexual Dimorphism
  • male larger
  • sexes colored or patterned differently
  • male more colorful
  • Range mass
    270 to 513 g
    9.52 to 18.08 oz
  • Range length
    32 to 40 cm
    12.60 to 15.75 in
  • Range wingspan
    16.9 to 17.5 cm
    6.65 to 6.89 in

Reproduction

Buffleheads generally form a mating pair that stays together during the season and in subsequent seasons. Less frequently, males pair with a second female after the first has finished laying her eggs. Courtship behavior occurs throughout the year and facilitates seasonal pairing of couples. Buffleheads use an array of physical displays and vocalizations during courtship. Males bob their heads and fly low over females to display their black and white underside and their pink legs, and then land with their feet straight as if water skiing. Paired birds display a “following” behavior where the female swims behind the male. The male stretches his neck upward and the female extends her neck back while she follows behind him. Buffleheads use displays both before and after copulation. Males also perform displays after threat or aggression from other males. (Gammonley and Heitmeyer, 1990; Gauthier, 1993; Usai, 1999)

Buffleheads breed once per year from late winter to early April. Breeding females lay a single clutch between late April and mid-May with an average of 9 eggs per clutch. Female buffleheads typically lay their eggs close to the same date each year, but second and third-year breeding females lay 4 to 9 days earlier than first year breeders. Their eggs are olive-buff colored. On average, they measure 50 by 36 mm and weigh 36.68 g. Females incubate the eggs for 30 days while males leave to molt. When leaving the nest to feed during the incubation period, females cover their eggs with feathers. (Gauthier, 1993; Knutsen and King, 2004; Lavers, et al., 2006)

Buffleheads use nests constructed by other species. Their nests are hollowed out cavities in trees usually within 15 m of a body of water and above flood plain level. Nests are often found in poplars and aspen, although pine trees are a favorite in the western United States. Nests are bare and buffleheads do not add material to their nests. Female buffleheads scout out their nest location up to a year in advance. If the desired nest is occupied when she returns, she searches for a new site with the male. Females only 1 year old have been observed searching for potential nest sites although they do not begin breeding until age 2. Two females have been documented sharing a same nest; however, one may evict the other that leaves the nest to feed. The average nest entrance is approximately 7 cm in diameter and the cavity diameter is 11.5 to 21 cm with a depth around 33.8 cm. Larger cavities are normally avoided because they are favored by goldeneyes (Bucephala islandica and Bucephala clangula). Goldeneyes can kill buffleheads in larger nests, but cannot enter the smaller entrances where buffleheads nest. (Ahlund, 2005; Gauthier, 1993)

Bufflehead chicks hatch after 28 to 35 days. They typically hatch within a span of 12 hours, but may take up to 36 hours from first to last. It is thought that late hatching eggs are laid during incubation. Precocial chicks are born with their eyes open and fully covered in down, with a mass around 23.8 g. Buffleheads are able walk as soon as their plumage dries out. Young buffleheads are nurtured intently during and after hatching. Newly hatched chicks live in the nest for 1 to 2 days and are then encouraged to jump from the nest hole. New mother buffleheads protect their brood for 3 to 6 weeks, at which point the young buffleheads are considered independent. (Gauthier, 1993; Knutsen and King, 2004; Lavers, et al., 2006)

Young ducklings are good swimmers, feeding on insects (92-100% of the time) on the water and dabbling for vegetation. Their diving abilities develop in the first few days and become the predominant mode of feeding. In fact, downy young spend 24% of their time diving. Growth rates vary among individuals which is typical of precocial birds. By day 20, the juvenile contour feathers begin to emerge with wing feathers appearing at day 23. Their belly feathers appear next and the head, back and neck feathers appear last. By day 40, males are apparently larger than their sisters. Plumage is complete after day 50 and the chicks fledge in 45 to 55 days. They reach reproductive maturity at 2 years. (Gauthier, 1993)

  • Breeding interval
    Buffleheads breed once per year from late winter to early April.
  • Breeding season
    Late winter to early April
  • Range eggs per season
    6 to 11
  • Average eggs per season
    8
    AnAge
  • Range time to hatching
    28 to 33 days
  • Range fledging age
    45 to 55 days
  • Range time to independence
    3 to 6 weeks
  • Average age at sexual or reproductive maturity (female)
    2 years
  • Average age at sexual or reproductive maturity (male)
    2 years

Male buffleheads stay with their mates during egg laying and for part of the incubation period. Females alone attend to the brood and defend their territory. They nurture their young for the first 2 to 3 weeks after hatching. The young huddle tightly together on both sides of the female on the shore or a floating log. Young buffleheads gather tightly and close behind their mother if she gives an alarm call. In British Columbia, 34% of broods had at least one exchange of young buffleheads between mothers, usually during a fight between them. Occasionally an entire brood is acquired by a female bufflehead that won a territorial fight. Bufflehead mothers protect their brood for up to 6 weeks, when the chicks are independent. (Ahlund, 2005; Gauthier, 1993; Usai, 1999)

  • Parental Investment
  • precocial
  • female parental care
  • pre-fertilization
    • protecting
      • male
  • pre-hatching/birth
    • protecting
      • male
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • provisioning
      • female
    • protecting
      • female

Lifespan/Longevity

Buffleheads live an estimated 2.5 years for males and 2.3 years for females. In rare cases, adults live very long and the record for the oldest adult is 18.7 years old. However, information on survivorship is limited. The most recent survivorship data available (1969 to 1973) was generated in New York State and was obtained by banding and recovering birds. From these data it was estimated that annual survivorship of females is between 61 to 73%, and 58 to 70% for males. Because the sample size was particularly small, (56 to 159 birds of each sex) the accuracy of these estimates is not known. (Gauthier, 1993; de Magalhaes and Costa, 2009)

  • Range lifespan
    Status: wild
    18.7 (high) years
  • Average lifespan
    Status: wild
    2.5 years
  • Average lifespan
    Status: wild
    2.5 years
  • Average lifespan
    Status: wild
    224 months
    Bird Banding Laboratory

Behavior

Buffleheads spend their time preening, swimming, diving, perching, flying and foraging. They seldom walk on land. They are moderately gregarious outside of the breeding season, often found in flocks to 5 to 10 and rarely in flocks of more than 50. Their principal daytime activity is foraging, comprising roughly 60 percent of their time. In the winter, buffleheads continue to forage through the night. They also migrate at night like many other ducks. Buffleheads have webbed feet that are used for propulsion during swimming and diving, as well as treading water when startled or to gain speed for flight. Nesting females perch at the opening of their nest cavities. Buffleheads preen and bathe while on the surface of the water and adults without nests may sleep on the surface of the water or on the shoreline. Females only sleep on land in bouts of 20 to 30 minutes, particularly during egg-laying periods and while protecting their young. (Gammonley and Heitmeyer, 1990; Gauthier, 1993)

Males sometimes exhibit aggressive behavior and displays, which is explained by two competing hypotheses. One suggests that territories are aggressively defended by male buffleheads to secure a food resource or to protect the breeding ground. The other hypothesis suggests that males are guarding the females, termed “mate-guarding.” Males demonstrate a threatening head-forward position to protect nesting territory sometimes accompanied by bumping and aggressive wing flapping. Bufflehead males may also dive or fly directly at an opponent to protect their defined territory. Other head postures such as an arching back or wing-flapping are considered a submissive response by the loser of a territorial battle. Once females lay their eggs, males do not defend as aggressively. After the hatchlings are out of the nest, males have already left for molting grounds. Female then become the defenders of their broods. Breeding territory of 0.33 hectares is most readily protected. (Gauthier, 1993; Usai, 1999)

Home Range

Territory size in British Columbia averages .56 hectares, but only .38 hectares is used with an intensely used territory of .38 ha. Males and females have different territories. Females claim a territory in the first few days following hatching on small ponds less than 400 m from the nest. This area is intensely defended by the female against goldeneyes (Bucephala clangula and Bucephala islandica) and other ducks. (Gauthier, 1993)

Communication and Perception

Buffleheads find prey underwater by sight, and they communicate through vocalizations and displays. Courting bufflehead males bob their heads and produce a loud raspy noise. In late winter and spring, they emit a low snarling grunts. Females make a loud deep throated vocalization while following males during leading displays. Females use a distinct low note to call their young which speeds up and increases in volume if she becomes distressed. Buffleheads display a head-forward posture and raised wing feathers when they are threatened or when protecting their territory or brood. Males protect their territory by posturing next to other male buffleheads. This includes a head-forward posture, flapping wings, and a raised tail. Once this display ends, they part ways. Wing beating following the toe to toe display is thought to be a sign of concession by the loser. (Gammonley and Heitmeyer, 1990; Gauthier, 1993)

  • Other Communication Modes
  • duets

Food Habits

Buffleheads primarily eat aquatic invertebrates and some seeds. Their freshwater diet consists of mostly insects like damselfly larvae, dragonfly larvae, midge larvae, water boatmen, mayfly larvae, caddisfly larvae and other insects. In saltwater habitats, a variety of arthropods and molluscs make up their diet. Buffleheads on the Pacific coast have been recorded consuming herring eggs in multi-species flocks and they occasionally eat fish like sculpins and ratfish. Prey is swallowed while submerged under the water. Buffleheads prefer to feed in water less than 3 meters deep. All of their food is acquired by diving except for downy young, who will dabble when first taking to the water. (Gauthier, 1993; Thompson and Ankney, 2002)

Buffleheads' diet varies seasonally and by habitat. In the fall, pondweed seeds, sedges, bulrushes, and mare’s tail become important to the bufflehead diet. The literature reports that avian egg shells and bones have also been found in their stomachs. Female buffleheads that consumed mostly gastropods during egg-laying were found to have higher egg production. Eggs were also found to be larger with stronger shells. Gastropod consumption peaks during incubation. (Gammonley and Heitmeyer, 1990; Thompson and Ankney, 2002)

  • Animal Foods
  • amphibians
  • fish
  • insects
  • mollusks
  • aquatic crustaceans
  • other marine invertebrates
  • Plant Foods
  • roots and tubers
  • wood, bark, or stems
  • seeds, grains, and nuts

Predation

Buffleheads are vulnerable to an assortment of predators that include birds of prey and mammals. Included in this list are peregrine falcons (Falco peregrinus), snowy owls (Nyctea scandiaca), and bald eagles (Haliaeetus leucocephalus), and possibly great horned owls (Bubo virginianus) and Cooper’s hawks (Accipiter cooperii). Weasels (Mustela) including mink (Neovison vison) and also squirrels (Sciuridae) and black bears (Ursus americanus) have been reported to feed on eggs in nest boxes. Female buffleheads are particularly vulnerable when perched on the nest, and eggs are vulnerable while females forage. (Gauthier, 1993)

Ecosystem Roles

Buffleheads disperse seeds in their environment. They compete for nests with Barrow’s goldeneyes (Bucephala islandica), common goldeneyes (Bucephala clangula), squirrels (Sciuridae), European starlings (Sturnus vulgaris) and northern flickers (Colaptes auratus). (Gauthier, 1993)

Like many ducks, buffleheads are prone to infection by a variety of parasites. When comparing buffleheads to other ducks, however, the abundance of parasitic species is modest. By examining the gizzards and intestines of adult buffleheads several species of roundworms, flukes, tapeworms, and thorny-headed worms were found. The roundworm species found were: Amidostomum acutum, Capillaria anatis, Capillaria contorta, Echinuria parva, Ecinuria uncinata, NematodaSchistorophus, Streptocara crassicauda, Streptocara formosensis, Tetrameres crami, Tetrameres fissipina, and Tetrameres spinosa. The flukes found were: Apatemon canadensis, Apatemon gracilis, Cotylurus strigeoides, Dendritobilharzia pulverulenta, Echinoparypthium recurvatum, Echinostoma trivolvis, Gyrosoma marilae, Maritrema obstipum, Notochotylus attenuatus, Odhneria odhneri, Philophthalmus gralli, Plagiorchis elegans, Prosthogonimus cuneatus, Pseudosplotrema, Psilochasmus oxyurus, Strigea, and Zygocotyle lunata. The tapeworms found were: Abortilepis, Aploparaksis, Cloacotaenia, Cloacotaenia megalops, Dicranotaenia multisticta, Diorchis bulbodes, Diploposthe laevis, Fimbriaria, Gastrotaenia cygni, Hymenolepis, Lateriporus skrjabini, Microsomacanthus collaris, Microsomacanthus melanittae, Microsomacanthus parvula, Platyscolex ciliata, Retinometra albeola, and Shistocephalus. Finally, the following thorny-headed worms found were: Corynosoma constrictum, Polymorphus acutis, Polymorphus marilis, and Polymorphus obtusus. (Ewart and McLaughlin, 1990; Gauthier, 1993; Gladden and Canaris, 2009)

Of particular interest is that buffleheads appear to be the only duck with the tapeworm Retinometra albeolae. Leeches (Theromyzon rude, Theromyzon tesulatum, and Theromyzon bifarium) may infest their upper respiratory tract as well as their eyes. Bufflehead ducklings are more prone to leeches. A trematode in the family Schistosomatidae has been observed in the arteries. Renal coccidia also have been observed. Additionally, avian cholera (Pasteurella multocida), avian malaria (Plasmodium relictum), and avian influenza all have been identified in buffleheads. The literature states that little is known about the impacts of parasites and disease on buffleheads. (Ewart and McLaughlin, 1990; Gauthier, 1993)

  • Ecosystem Impact
  • disperses seeds
Commensal/Parasitic Species
  • roundworms Amidostomum acutum
  • roundworms Capillaria anatis
  • roundworms Capillaria contorta
  • roundworms Ecinuria parva
  • roundworms Echinuria uncinata
  • roundworms Schistorophus
  • roundworms Streptocara crassicauda
  • roundworms Streptocara formosensis
  • roundworms Tetrameres crami
  • roundworms Tetrameres fissipina
  • roundworms Tetrameres spinosa
  • flukes Apatemon canadensis
  • flukes Apatemon gracillis
  • flukes Cotylurus strigeoides
  • flukes Dendritobilharzia pulverulenta
  • flukes Echinoparypthium recurvatum
  • flukes Echinostoma trivolvis
  • flukes Gyrosoma marilae
  • flukes Maritrema obstipum
  • flukes Notochotylus attenuatus
  • flukes Odhneria odhneri
  • flukes Philophthalmus gralli
  • flukes Plagiorchis elegans
  • flukes Prosthogonimus cuneatus
  • flukes Pseudosplotrema
  • flukes Psilochasmus oxyurus
  • flukes Strigea
  • flukes Zygocotyle lunata
  • tapeworms Abortilepis
  • tapeworms Aploparaksis
  • tapeworms Cloacotaenia
  • tapeworms Cloacotaenia megalops
  • tapeworms Dicranotaenia multisticta
  • tapeworms Diorchis bulbodes
  • tapeworms Diploposthe laevis
  • tapeworms Fimbriaria
  • tapeworms Gastrotaenia cygni
  • tapeworms Hymenolepis
  • tapeworms Lateriporus skrjabini
  • tapeworms Microsomacanthus collaris
  • tapeworms Microsomacanthus melanittae
  • tapeworms Microsomacanthus parvula
  • tapeworms Platyscolex ciliata
  • tapeworms Retinometra albeola
  • tapeworms Shistocephalus
  • thorny-headed worms Corynosoma constrictum
  • thorny-headed worms Polymorphus acutis
  • thorny-headed worms Polymorphus marilis
  • thorny-headed worms Polymorphus obtusus

Economic Importance for Humans: Positive

During the winter and fall months the habitat of buffleheads is prime duck hunting range, so they are a target for hunters. Buffleheads make up 1 to 1.5% of all ducks killed in the U.S. and 1.5 to 2% in Canada. During 2009, in the Atlantic Flyway of Georgia, Maine and Maryland, 17,947 buffleheads were harvested. In 2008, there were 27,154 were harvested. Buffleheads also eat many types of insects, some of which are pests to humans. (Gauthier, 1993; Raftovich, et al., 2010)

  • Positive Impacts
  • food
  • controls pest population

Economic Importance for Humans: Negative

There are no adverse effects of Bucephala albeola on humans.

Conservation Status

Buffleheads are listed as least concern on the IUCN Red List and do not have special status on US government lists. Previously, they were threatened by overshooting at the end of the 19th and beginning 20th century. Toxic contaminants are a current threat as well. Buffleheads collected around Long Island, NY, had low levels of polychlorinated biphenyls (PCBs) and mercury in their bodies. However, when compared to other dangers, habitat degradation is probably their biggest threat. Aspen nesting habitat has been replaced over the last 100 years in western North America with agricultural land, and clear-cutting for lumber continues to reduce the availability of nesting habitat. Nest boxes have been installed in some areas to supplement nesting habitat. It is important that these boxes be placed in conifer-heavy areas and the box openings be the correct size and mimic their natural nesting preferences. These specifications limit competition with other cavity-nesters. (Gauthier, 1993)

Contributors

John Huth (author), Radford University, Karen Powers (editor), Radford University, Kiersten Newtoff (editor), Radford University, Melissa Whistleman (editor), Radford University, Catherine Kent (editor), Special Projects.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

arboreal

Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

bog

a wetland area rich in accumulated plant material and with acidic soils surrounding a body of open water. Bogs have a flora dominated by sedges, heaths, and sphagnum.

brackish water

areas with salty water, usually in coastal marshes and estuaries.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

crepuscular

active at dawn and dusk

diurnal
  1. active during the day, 2. lasting for one day.
duets

to jointly display, usually with sounds in a highly coordinated fashion, at the same time as one other individual of the same species, often a mate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

estuarine

an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.

female parental care

parental care is carried out by females

food

A substance that provides both nutrients and energy to a living thing.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

freshwater

mainly lives in water that is not salty.

insectivore

An animal that eats mainly insects or spiders.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

marsh

marshes are wetland areas often dominated by grasses and reeds.

migratory

makes seasonal movements between breeding and wintering grounds

molluscivore

eats mollusks, members of Phylum Mollusca

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

scrub forest

scrub forests develop in areas that experience dry seasons.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

suburban

living in residential areas on the outskirts of large cities or towns.

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

tactile

uses touch to communicate

taiga

Coniferous or boreal forest, located in a band across northern North America, Europe, and Asia. This terrestrial biome also occurs at high elevations. Long, cold winters and short, wet summers. Few species of trees are present; these are primarily conifers that grow in dense stands with little undergrowth. Some deciduous trees also may be present.

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

visual

uses sight to communicate

young precocial

young are relatively well-developed when born

References

Ahlund, M. 2005. Behavioural tactics at nest visits differ between parasites and hosts in brood-parasitic duck. Animal Behaviour, 70/2: 433-440.

Braune, B., B. Malone. 2006. Mercury and selenium in livers of waterfowl harvested in Northern Canada. Archives of Environmental Contamination and Toxicology, 50/2: 284-289.

Custer, C., T. Custer. 200. Organochlorine and trace element contamination in wintering and migrating diving ducks in the southern Great Lakes, USA, since the zebra mussel invasion. Environmental Toxicology and Chemistry, 19/11: 2821-2829.

Dugger, B., K. Dugger, L. Fredrickson. 2009. "The Birds of North America Online" (On-line). Accessed April 08, 2012 at http://bna.birds.cornell.edu/bna/species/098.

Eadie, J., M. Mallory, H. Lumsden. 1995. "The Birds of North America Online" (On-line). Accessed April 08, 2012 at http://bna.birds.cornell.edu/bna/species/170.

Evans, M., D. Lank, W. Boyd, F. Cooke. 2002. A comparison of the characteristics and fate of Barrow’s goldeneye and bufflehead nests in nest boxes and natural cavities. The Condor, 104/3: 610-619.

Ewart, M., J. McLaughlin. 1990. Helminths from spring and fall migrant bufflehead ducks (Bucephala albeola) at Delta, Manitoba, Canada. Canadian Journal of Zoology, 68/10: 2230-2233.

Gammonley, J., M. Heitmeyer. 1990. Behavior body condition, and foods of buffleheads and lesser scaups during spring migration through the Klamath Basin, California. Wilson Bulletin, 102/4: 672-683.

Gauthier, G. 1993. "The Birds of North America Online" (On-line). Bufflehead (Bucephala albeola). Accessed February 08, 2012 at http://bna.birds.cornell.edu/bna/species/067.

Gladden, B., A. Canaris. 2009. Helminth parasites of the bufflehead duck, Bucephala albeola, wintering in the Chihuahua Desert with a checklist of helminth parasites reported From this host. Journal of Parasitology, 95/1: 129-136.

Knutsen, G., J. King. 2004. Bufflehead breeding activity in south-central North Dakota. The Prairie Naturalist, 36/3: 187-190.

Lavers, J., J. Thompson, C. Paszkowski, C. Ankney. 2006. Variation in size and composition of bufflehead (Bucephala albeola) and Barrow’s goldeneye (Bucephala islandica) eggs. The Wilson Journal of Ornithology, 118/2: 173-177.

Martin, K., K. Aitken, K. Wiebe. 2004. Nest sites and nest webs for cavity-nesting communities in interior British Columbia, Canada: Nest characteristics and niche partitioning. The Condor, 106/1: 5-19.

McKinney, R. 2004. Habitat relationships of waterfowl wintering in Narrgansett Bay. Rhode Island Naturalist, 11/2: 3-6.

McKinney, R., S. McWilliams. 2005. A new model to estimate daily energy expenditure for wintering waterfowl. The Wilson Bulletin, 117/1: 44-55.

Raftovich, R., K. Wilkins, K. Richkus, S. Williams, H. Spriggs. 2010. "Migratory bird hunting activity and harvest during the 2008 and 2009 hunting seasons." (On-line). Accessed April 18, 2012 at http://www.fws.gov/migratorybirds/NewsPublicationsReports.html.

Schummer, M., S. Badzinski, S. Petrie, Y. Chen, N. Belzile. 2010. Selenium accumulation in sea ducks wintering at Lake Ontario. Archives of Environmental Contamination and Toxicology, 58/3: 854-862.

Schummer, M., S. Petrie, R. Bailey. 2008. Dietary overlap of sympatric diving ducks during winter on northeastern Lake Ontario. The Auk, 125/2: 425-433.

Thompson, J., C. Ankney. 2002. Role of food in territoriality and egg production of buffleheads (Bucephala albeola) and Barrow’s goldeneyes (Bucephala islandica). The Auk, 119/4: 1075-1090.

Usai, M. 1999. Bufflehead: Diving duck winters in New York. New York State Conservationist, 53/4: 10-12.

de Magalhaes, J., J. Costa. 2009. A database of vertebrate longevity records and their relation to other life-history traits. Journal of Evolutionary Biology, 22/8: 1770-1774.