Although first described from a resident population in Iceland, whence its scientific name, Barrow's Goldeneye is chiefly a bird of the western montane region of North America. Once referred to as the Rocky Mountain Goldeneye, this species is generally restricted to areas west of the Continental Divide, with small numbers found in the eastern Canadian Maritime Provinces and United States during winter. Speculation about the location of a disjunct breeding population in eastern North America previously centered on the treeless arctic regions of the northern Ungava Peninsula in northeastern Québec and Labrador. However, nesting in these areas has not been confirmed and is doubtful. An important breeding location was recently located in the forested regions of the Laurentian Highlands in southeastern Québec.
Named for John Barrow (1764-1848) of the British Admiralty in recognition of his support of arctic exploration, Barrow's Goldeneye breeds on interior fresh-water lakes and ponds. Like other sea ducks (tribe Mergini), however, it typically spends fall and winter on salt water or estuaries along the coast. Adults and juveniles feed predominantly on invertebrates, although diet shifts dramatically between the breeding season (when aquatic insects make up most of the diet) and winter (when marine mollusks and occasionally fish eggs become major prey items).
Like its smaller congeners-the Common Goldeneye (Bucephala clangula) and the Bufflehead (B. albeola)-Barrow's Goldeneye is a cavity-nesting duck that depends heavily on the availability of large cavities. Nest boxes have been a useful management tool to supplement natural cavities. Barrow's Goldeneye is the most aggressive of all 3 species of Bucephala, and both males and females defend site-specific pair and brood territories, respectively. This species dominates Buffleheads and Common Goldeneyes in interspecific interactions, and also defends territories against other species of waterfowl; females with broods have been reported to kill ducklings of conspecifics and other species.
Barrow's Goldeneye is potentially long-lived for a duck, with a maximum reported longevity of 18 yr in the wild. In British Columbia, most females do not breed until their third year. Pair bonds are long-term, and both males and females exhibit philopatry to breeding and wintering grounds. Natal philopatry appears to be high among females. Complex social interactions occur among females, including frequent conspecific brood parasitism and posthatch brood amalgamation (crèching behavior).
Barrow's Goldeneye populations appear to be stable throughout most of their range, although robust estimates of total population size are not available. Because of the restricted distribution of this species (60% of the world population breeds and winters in a single Canadian province) and relatively small global population (estimated <200,000 birds), this species warrants careful monitoring. Potential threats include oil spills on wintering areas, accumulation of heavy metals in prey items, recreational development on breeding lakes, and loss of nesting habitat (especially large nesting trees) due to logging.
Until recently, relatively little was known of the ecology of this species in North America other than the early studies of Munro ( Munro 1918 , Munro 1939c ) and unpublished work of Mary Jackson (in Bellrose 1980 ). In the past 2 decades, however, several new studies have been completed on both breeding ( Savard 1986b , Eadie 1989 , Thompson 1996f ) and postbreeding ecology ( Van De Wetering 1997 ). New research using satellite telemetry has confirmed a breeding population in Québec and has provided important insights on winter ecology, molt migration, and location of key molting sites in the eastern population (Savard Savard 1990 , Savard 1996a ; Savard and Dupuis 1999 ; Robert et al. Robert et al. 1999a , Robert et al. 1999b , Robert et al. 2000 ). The conservation status of the eastern population is currently under review.