- Gavia immer
ALSO KNOWN AS GREAT NORTHERN DIVER
Identification
Length 65-91cm. Wingspan 137cm. The most numerous diver in North America and a familiar bird on its breeding grounds. Adult breeding: Black above with bold white chequer-spots, white below. Head black with collar of short vertical white stripes, broadest on hindneck and half-necklace of white spots below chin. Adult non-breeding: blackish-grey above and white below but lacks sharp contrast seen in Black-throated Diver G. arctica. Head and neck usually darker than back shows indistinct half-collar at base of hindneck, also usually lacks white flank patch. Best distinguished from smaller species by heavy build and bill and from Yellow-billed Diver G. adamsii by straighter, usually darker bill, held horizontally. Some Great Northerns show whitish bills but culmen is always dark.
Range
Common and widespread across North America breeding from Alaska south to northern Washington and east to the Great Lakes and New England. Absent from north-central Arctic Canada and south-central Canada. Also breeds in Greenland and Iceland. Possibly breeds regularly on Bear Island and has bred in Scotland.
Winters in North America from the Aleutians south to northern Mexico in the west and from Newfoundland to the Gulf Coast in the east. European birds winter from Iceland and northern Norway south to north-west France with vagrants recorded on the Azores, on the Mediterranean coast of North Africa and in Ukraine.
Habitat
Breeds on medium-large, deep lakes in tundra and forest areas. Winters at sea in bays and estuaries, sometimes large inland waters.
==VOICE== Familiar loud wailing and yodelling calls during the breeding season.
Behaviour
Breeds late-May or early June to September. Nests beside water often on an island or spit, a shallow scrape or more rarely a substantial mound of vegetation built in shallow water in reedbeds. Eggs: 2 (1 in replacement clutch), olive-brown, sometimes more greenish with sparse black blotches (90 x 57mm). Incubated by both sexes for 29-30 days. Young tended by both sexes, feed themselves at 40 days and fly at about 72 days
DIET
Fish, also molluscs and crustaceans caught during 60-120 second dives.
Subspecies No subspecies usually recognised but birds from western Canada are sometimes separated as race elasson.
Bird Song
<flashmp3>Gavia immer (song).mp3</flashmp3>
Listen in an external program
