In Svalbard long-tail ducks eat mussels, crustaceans and insect larvae. The long-tailed duck (Clangula hyemalis), formerly known as oldsquaw, is a medium-sized sea duck that breeds in the tundra and taiga regions of the arctic.
Their diet consists mainly of invertebrates, but they also feed on some plant matter. They show considerable variation in habitat use and dive to various depths. Outside the breeding season long-tailed ducks stay mainly in coastal waters. The territory usually includes a freshwater pool where intense courtship behaviour occurs. The males are very territorial and occupy the same area every year. In winter, males are predominately white with brown markings. Their heads are small and round with straight-ish foreheads. The eggs are covered with down when left, but are still vulnerable to predators. The long-tailed duck is a small sea duck and as the name suggests has long tail feathers. The female usually flew out to sea, but was back after only three or four minutes. Studies performed in Ny-Ă…lesund showed that incubating females left the nest three or four times during each 24 hour period. Incubating female long-tailed ducks remain on the nest until the last possible moment when an intruder approaches, similar to common eider females. The nests are often placed in colonies of arctic terns, which affords them protection against predators such as the Arctic fox, glaucous gull and Arctic skua. Several pairs may nest close together though the species is not regarded as being a colonial breeder. Complex plumages, but in winter, males with. The long-tailed duck breeds on the tundra, usually near freshwater ponds and lakes. Small brown, black and white duck, with rounded head and short stubby bill. The male emits characteristic, melodic notes while the female makes fainter barking noises. The colour markings on the neck and head vary through the year.
The female in nesting plumage has a dark brown back and white under-parts and brown-black head with a large white patch around the eye and down the side of the neck. In spring and autumn it has an intermediate transitional plumage. In winter plumage it has a white head, neck, belly and parts of the back, while the breast and the wings are brown. The male (in nesting plumage) has a dark brown back, white belly and brown-black neck and head with a large white patch around the eye. It is a sexually dimorphic species in which the male is larger and more. The male has central tail-feathers that are up to 13 cm long, which gives rise to the common name for this duck. The long-tailed duck is a small diving duck with a short bill and small head. Adult weights vary between 600 and 900 g. Males are 53 cm long while females are approximately 40 cm long. It is a sexually dimorphic species in which the male is larger and more brightly coloured than the female. The long-tailed duck is a small diving duck with a short bill and small head.