the black guillemot is a medium-sized seabird distributed throughout arctic regions of the atlantic. they are distinguishable by their feet, bills, and the inside of their mouths, all of which are a bright coral red. there is no visible difference between the sexes. in the summer, this guillemot is almost entirely solid black. in the winter, they display a mottled gray-white pattern, as do juveniles. they feed on fish, crustaceans, eels, and other aquatic food sources. they feed by diving below the surface to snatch their prey and/or collect plant material as food. they nest in rocky crevices and outcroppings of cliffs. the guillemot is a social bird and is often found in large colonies.