143516 Guillemot Uria aalge L 42cm. Familiar seabird that nests in densely packed breeding colonies. Swims well and flies on whirring wingbeats. Sexes are similar. Adult in summer has chocolate-brown head and upperparts (darkest in N birds) and white underparts. Bill is dark and dagger-like; so-called ‘Bridled Guillemot’ has white ‘spectacle’ around eye. In winter, has white on cheeks and throat but black line running back from eye. Voice Utters growling calls at breeding colonies. Status Locally numerous at seabird colonies with precipitous cliff ledges. Moves offshore outside breeding season. Suffers badly in oil spills.