The black guillemot is a medium sized auk. Black guillemots can be found in the Svalbard area all year round where there is open water.
The black guillemot is a medium sized auk.
When in its breeding plumage it is very distinctive. The birds are dark brown-black with a large white patch on the wing; and the black and white feathers are in marked contrast to the bright red gape and feet of the birds. The bill is black.
The sexes are similar in appearance. Adult birds are approximately 34 cm long and weigh 350–450 g. The winter plumage is predominantly white on the head, neck and under-parts, while there are black and white bars across the crown, neck, back and flanks.
Five subspecies of black guillemots are recognized; the Svalbard population belongs to the arctic sub-species mandtii, which is characterized by a larger white patch on the wing and by lighter colouring of the winter plumage.
Juvenile birds resemble the adult in winter plumage, but the upper-parts of their bodies are darker and browner. Yearlings in summer plumage can be distinguished from adults by their variegated brown wing patch and variegation of the white patches on the under-parts. The rest of their plumage is more brown than black.
The call of the black guillemot is a light, wailing whistle.
The black guillemot has a nearly circumpolar distribution from the Canadian Arctic via Greenland and Iceland to the British Isles and the Scandinavian coastline (including the Bay of Bothnia) through to the Russian Arctic where it breeds along the whole coastline.
Black guillemots are more sedentary than other auks and are seldom observed outside their breeding range or in offshore waters. In Svalbard, the black guillemot is a common breeding bird in all parts of the archipelago. It breeds in small, scattered, loose colonies along the coast and on islands, but single nests are also found up to several kilometres inland. A total of 202 colonies/breeding areas are known in the archipelago.
Black guillemots can be found in the Svalbard area all year round where there is open water. However, most of the birds that breed in Svalbard probably winter close to the ice edge off the archipelago and in the Greenland and Barents Seas.
The number of black guillemots in coastal waters around Svalbard increases in March and April and decreases once again in late autumn.
The black guillemot is associated with inshore waters during the breeding season, more so than the other auks. It finds most of its food in shallow waters. Individuals that are seen pelagically during the summer are mostly non-breeding birds.
Although the species is traditionally the least sociable of the auks and in most places nests as solitary pairs, loose colonies of up to several hundred pairs are found in Svalbard. They also nest in association with other seabird species in some areas.
The black guillemot feeds on fish and crustaceans. It is opportunistic in its food choice and switches rapidly between prey types as their availabilities change. In Svalbard, benthic fish such as sculpins and blennies are common prey in coastal areas; in the drift-ice mostly polar cod and crustaceans are consumed.
Life history and reproduction
The black guillemot nests in a rocky crevice, under stones or in screes, where they are inaccessible to predators. The nest site can be close to sea level or high up in bird-cliffs.
The one or two (usually two) eggs are light greyish with dark speckles and blotches and are laid directly onto the ground. Incubation is by both sexes and lasts 28–31 days.
The black guillemot is the only paleoarctic alcid species that rears more than one chick. The ability to do so is probably related to its inshore feeding habit. It avoids long-distance flights between the feeding and breeding areas. The nestlings are covered in a black down and remain in the nest until they attain their juvenile plumage.
The chicks are fed by both parents with various species of fish and crustaceans, and fledge after 30–40 days. After fledging, the young are independent of the parents.
Management status and monitoring
Because of its dispersed breeding pattern and hidden nests, the black guillemot is difficult to study or census in the breeding season. No detailed counts have been performed in Svalbard, but the breeding population has been estimated roughly at 20 000 breeding pairs. The status of the population is unknown.
The breeding population in the Barents Sea region is estimated to be 60,000–80,000 pairs, The European population numbers some 130 000 pairs and the global population is 260,000–410,000 pairs, although this estimate is based mainly on rough estimates throughout most of the range.
Black guillemots are harvested in Svalbard in low numbers.