Barrow’s goldeneye (Bucephala islandica), is a medium-sized duck of the Anatidae family in the Anseriformes order. It inhabits mainly northwest North America from southern Alaska through the U.S. Pacific Northwest, with small populations wintering in eastern Canada and the United States (Eadie, et al 2000). B. islandica usually spends the summer breeding season on cold inland lakes and ponds, normally in forested country, and in winter moves to coastal inlets, bays, and estuaries. The Barrow's goldeneye prefers small bodies of water that are clear of vegetation and have few fish to compete for insects (Kauffman 2018; Seattle Audubon 2018).
Female Barrow’s goldeneyes have brown heads, light gray feathers on their breast, and dark gray or black feathers on their rump. The bill of the female is mostly yellow, and is smaller than the mostly black, yellow-tipped bill of the otherwise very similar common goldeneye (Seattle Audubon 2018). Male Barrow's goldeneyes have iridescent purple heads that look black when not in the sun, and prominent, crescent-shaped white spots near the sides of their black bill. Their backs are mostly black with white spots. Juveniles are mostly gray with brownish heads similar to females, but with less contrast between the head and body colors. Both sexes of the Barrow's goldeneye are between 43-48 cm and weigh between 480-1320 g (Seattle Audubon 2018).
At night, during fall and winter,groups ranging from 5 to 50 individuals sleep on freshwater lakes and sheltered marine coves. These groups break up into pairs or small groups at daybreak to feed. During summer, breeding females are often observed alone or with a mate or brood; nonbreeding females occur in small groups. Males molt in scattered small groups but may form large flocks of several hundred. Migration of inland-nesting birds tends to occur in small flocks (Eadie, et al 2000). They feed mainly on aquatic insects such as dragonfly and caddisfly larvae during the summer, while in winter they eat mollusks, crustaceans, and fish in coastal waters, usually catching their food by diving or swimming. During the summer and fall, they also consume plant material, especially pondweeds (Seattle Audubon 2018; Kaufman 2018).
Barrow's goldeneyes usually form mating pairs in winter. The male’s courtship display involves a turning and pumping of its head, as well as some flapping of its wings. After mating, the female will select a nesting site, often found in large tree cavities, holes, and rock tunnels. The nest the female makes has a slight concaved shape and is lined with sticks, down, and other materials. They usually lay around 7-10 eggs, which range from pale olive to blue-green. The incubation period of the eggs is around 28-34 days, with juveniles leaving the nest about 1-2 days after hatching. The ducklings learn how to fly at about 8 weeks (Seattle Audubon 2018).
B. islandica is very territorial and aggressive and are a main predator in its ecosystem. They are, in turn, prey for several animals, ranging from black bears and raccoons to hawks. Currently they appear to be in little danger regarding population decline (Bird Life International, 2016).
Barrow's goldeneye (Bucephala islandica) is a medium-sized sea duck of the genus Bucephala, the goldeneyes. This bird was named after Sir John Barrow. The genus name is derived from Ancient Greek boukephalos, "bullheaded", from bous, "bull " and kephale, "head", a reference to the bulbous head shape of the bufflehead. The species name islandica means Iceland.
Barrow's goldeneye was formally described in 1789 by the German naturalist Johann Friedrich Gmelin in his revised and expanded edition of Carl Linnaeus's Systema Naturae. He placed it with the ducks, geese and swans in the genus Anas and coined the binomial name Anas islandica.[2] Gmelin based his description on the "Hravn Oend" that had been briefly described in 1776 by Danish naturalist Otto Friedrich Müller.[3][4] Barrow's goldeneye is now placed with the common goldeneye and the bufflehead in the genus Bucephala that was introduced in 1858 by American naturalist Spencer Baird.[5][6] The genus name is derived from Ancient Greek boukephalos, meaning "bullheaded", from bous "bull", and kephale, "head. The specific epithet islandica is for Iceland.[7] The species is monotypic: no subspecies are recognised.[6]
Adults are similar in appearance to the common goldeneye. On average, adult males are 19.2 in (49 cm) long and weigh 2.13 lb (970 g); females are typically 17 in (43 cm) long and weigh 1.31 lb (590 g).[8] The Barrow's goldeneye has a wingspan of 27.6-28.7 in (70-73 cm).[9] Adult males have a dark head with a purplish gloss and a white crescent at the front of the face. Adult females have a mostly yellow bill. The male Barrow's goldeneye differs from the male common goldeneye in the fact that the common goldeneye has a round white patches on the face, less black on the back of the bird, a greenish gloss, and a larger bill. For the females, the common goldeneye has a less rounded head, and a bill in which only the tip is yellow.[10]
The Barrow's goldeneye is a relatively quiet bird that generally only makes vocalizations during the breeding season and courtship. These can include low volume squeaks, grunts and croaks. During flights, the fast movement of the bird's wings creates a low whistling sound.[11]
Their breeding habitat consists of wooded lakes and ponds primarily in northwestern North America, but also in scattered locations in eastern Canada and Iceland. Females return to the same breeding sites year after year and also tend to use the same nesting sites. The males stay with their mate through the winter and defend their territory during the breeding season, then leave for the molting site. Mating pairs often stay intact even though the male and female are apart for long periods of time over the summer during molting times. The pair then reunites at wintering areas.[12]
In Iceland the bird is known as húsönd (house-duck); it is a common species of the Lake Mývatn in the north of the country.
There have been three records of vagrants from Scotland,[13] the only records of this species accepted as wild in Europe outside of Iceland.[14]
They are migratory and most winter in protected coastal waters or open inland waters. Barrow's goldeneye, along with many other species of sea ducks, rely on urbanized, coastal estuaries as important places on their migration patterns. These estuaries provide excellent wintering and stopping places during the ducks' migration.[15] It is an extremely rare vagrant to western Europe and to southern North America.[16]
These diving birds forage underwater. They eat aquatic insects, crustaceans and pond vegetation. The main staples of the bird's diet are Gammarus oceanicus and Calliopius laeviusculus, which are both marine crustaceans. A large part of their diet consists of mussels and gastropods.[17]
The Barrow's goldeneye is considered an arboreal bird species because much of its nesting is done in cavities found in mature trees. The birds will also nest in burrows or protected sites on the ground.[18] Barrow's goldeneyes tend not to share habitat with the much more numerous common goldeneye. Barrow's goldeneye tend to be territorial towards other birds venturing into their domain. This is especially true among the drakes. Confrontations may occur in the form of fighting. Drakes often do a form of territorial display along the boundaries of their territory. This is both true on land and in the water. These territorial displays average about 6 minutes in length and often trigger other males to perform their own show.[19]
Very little is known about the breeding sites and patterns of the Barrow's goldeneye. After the breeding season, the birds migrate to specific molting sites to undergo molting, the loss and regeneration of feathers which causes them to be flightless for anywhere from 20–40 days. These molting sites are often wetlands that are more drought resistant and plentiful in food, along with being less influenced by humans and predators.[20]
The Barrow's goldeneye was greatly affected by the Exxon Valdez oil spill in 1989. The spill greatly impacted the bird's wintering areas, and numbers of the birds in these areas decreased after the spill. The birds' exposure to the oil spill mainly occurred in the shallow water mussel beds along the coast.[21]
male and female goldeneye, Rideau River, Ottawa
male
male
female
Barrow's goldeneye (Bucephala islandica) is a medium-sized sea duck of the genus Bucephala, the goldeneyes. This bird was named after Sir John Barrow. The genus name is derived from Ancient Greek boukephalos, "bullheaded", from bous, "bull " and kephale, "head", a reference to the bulbous head shape of the bufflehead. The species name islandica means Iceland.
