Breeding birds: 19,000 pairs
Wintering birds: 58-80,000 birds
Family: Auks, Murres, And Puffins
In breeding plumage, the adult black guillemot is entirely black or very dark brown except for a white patch on the uppwerwing and white undertail coverts. Some birds may occasionally be missing the wing patches.
It has a thin, pointed black bill with a bright red mouth-lining, dark brown eyes, bright red legs and webbed feet with black claws.
Out of breeding plumage, the black guillemot is light grey with white wing patches. Its head and underparts are white, and its upperparts are speckled with light grey, black, and white.
The juvenile black guillemot is similar to adults in winter, but its upperwing patches are mottled and the wing coverts have brown tips.
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The black guillemot breeds between late May and mid June and produces 1 brood per season. It forms monogamous pair bonds that last for several seasons, and each year, pairs return to the same breeding grounds where they engage in a courtship ritual with the male circling the female at sea or on land.
It nests either alone or in small, scattered colonies. The nest is typically located in a rock crevice at the base of a cliff or in a cavity along the cliff face. While it is occasionally concealed by vegetation, it is most often placed directly on the ground.
The black guillemot lays 1-2 dull white or pale green eggs with dark markings which are incubated by both adults for 28-32 days. Chicks are semi-precocial and covered in dark down, and are fed by both parents until they fledge at 30-40 days. They reach sexual maturity at 3-4 years, when they return to their natal colony.
Black guillemots eat mainly fish but further north will also feed on crustaceans.
Black guillemots can be seen in the UK all year round. They are found down the west coast of Scotland and the North West of England, along the Northern Ireland coast, and on the Isle of Man.
Black guillemots carry fish crosswise in their bills, sometimes for hours at a time, a behaviour described by Edmund Selousin his book The Bird Watcher in the Shetlands published in 1905.
