The Guillemot is best identified by its bill: long, wholly dark and gently tapering to a point. In flight they are slimmer and browner than Razorbills. In winter Guillemots have a pale throat and cheeks, marked by a characteristic dark line behind the eye like the arm of a pair of spectacles. Guillemots have distinctively streaked flanks which aid identification.
They breed on cliffs and rocky coasts. Wintering at sea, and around coasts.