Black Guillemot

The black guillemot is a medium-sized bird with adults normally 30 to 32 centimetres (12 to 12+1⁄2 inches) in length and with wingspans of 52 to 58 cm (20+1⁄2 to 23 in). The bodyweight can range from 300 to 460 grams (10+1⁄2 to 16 ounces). Adults have both summer and winter plumage and there is no sexual difference in this that can be identified in the field. The English common name "Black Guillemot" references their strikingly black breeding summer plumage which is totally black except for a large white patch on the upper side of their wings. During the summer plumage, their legs, feet and inside of the mouth are all a bright coral-red, and their beak is black. Adults lose their summer plumage in an early fall moult where their upper plumage become barred with light grey and white, their head is a pale grey, their underparts white, and legs and feet a pale red. They retain their white wing patch, black beak and red inside their mouth. The call in the breeding season is a high whistle. The red gape is also prominent then. Juveniles and immatures can easily be identified by the spotting of the white wing patch with grey or brown feathers and is easy to see even at far distances in the field.

The black guillemot is a circumpolar species distributed in the boreal, low arctic and high arctic regions of the north Atlantic and arctic oceans and breeding between 43° and 82°N. The 5 listed subspecies inhabit different parts of this range. In North America, they can be found as far south as the Gulf of Maine and New England and across parts of the northern coast of North America as far as Alaska, where they are replaced by the pigeon guillemot in the North Pacific. In Europe and Asia, they are found from the British Isles and Northward across the northern coast of Asia. They are one of the few birds to breed on Surtsey, Iceland, a new volcanic island. It is a fairly common breeding bird around the coast of Ireland, and in western and northern Scotland. In the remainder of Britain, they only breed at St. Bees Head in Cumbria, the Isle of Man and on east Anglesey in north Wales. Approximately 40% of the population breeds in the high arctic where the largest colonies are found, 30% in the low arctic, and 30% in boreal waters. In the winter, some of the birds in the high arctic waters are forced south by the winter ice making them seasonal migrants, but in more temperate zones the species is essentially resident. Typically restricted to rocky shores, black guillemots utilize the cliffs, crevices and boulders for their nests, hunting the inshore waters for benthic prey. …

One of the early ornithologists that described aspects of the behaviour of the black guillemot was Edmund Selous (1857–1934) in his book The Bird Watcher in the Shetlands (1905). In the chapter titled 'From the Edge of a Precipice' he writes for instance that sometimes the black guillemots carry a fish they have caught in their beak for hours. He also gives further details about the behaviour. Black guillemots are coastal foragers with diets typically associated with benthic and kelp-forest prey. They dive between 15-20m to catch their prey, but can dive to a depth of at least 43m. They use their wings to propel themselves forward and their feet to steer. Small prey are swallowed underwater whole. Guillemots bring larger prey to the surface to soften in their bill before swallowing whole. Guillemots are single-prey loaders, meaning they bring single prey items back to their chicks during the chick-rearing period. This limits the spatial range that parents can forage for food, as chicks must receive a high number of energy-rich prey items throughout each day. Black guillemot diets include sculpins, butterfish, rock gunnel, northern sandlance, herring, jellyfish, mollusks, and other small crustaceans.