Common Murre

The common murre (Uria aalge), also known as the common guillemot, is a large auk that inhabits the cooler waters of the Northern Hemisphere. It is found along the coasts of the North Atlantic and North Pacific, ranging from the eastern seaboard of North America and Western Europe to the western coasts of North America and Asia. The common murre is approximately 38-46 cm (15-18 in) in length with a wingspan of 61-73 cm (24-29 in). Adult common murres are characterized by their black head, back, and wings contrasted with a white underbelly. In winter, their face becomes white with a distinct black line from the eye to the ear. They are similar to the thick-billed murre (Uria lomvia), but the common murre has a thinner bill and lack the distinct white gape stripe of the thick-billed murre.

Common murres inhabit coastal waters and open oceans, usually not far from land. They are typically found on rocky cliffs during the breeding season and at sea for the rest of the year. This species feed primarily on small fish such as capelin, sand lance, herring, and juvenile cod, as well as invertebrates like squid and crustaceans. They are adept divers, capable of reaching depths of up to 180 meters, although they usually feed at depths less than 50 meters. Their foraging technique involves diving from the surface and using their wings to swim underwater in pursuit of prey.

Common murres are migratory birds that travel significant distances between their breeding and wintering grounds. After the breeding season, which occurs from May to July, they disperse widely across the ocean. Birds from North Atlantic colonies may travel as far south as the Mediterranean Sea and the eastern coast of North America, while Pacific populations migrate to the coastal waters off Japan and California. Migration typically occurs from late summer through fall, and they return to breeding sites in early spring.

Breeding season for common murres begins in May and extends through July. They nest in dense colonies on steep, rocky cliffs where they lay a single egg directly on the bare rock. The egg is pointed at one end, which helps prevent it from rolling off the cliff ledge. Both parents share incubation duties, which last for about 30-35 days. After hatching, the chick remains on the cliff ledge for about 15-25 days before fledging. During this time, it is fed by both parents. Once fledged, the chick goes to sea with the male parent, where it continues to be cared for and fed for several weeks until it is independent.

The common murre is currently listed as least concern by the IUCN Red List, though some local populations have experienced declines due to factors such as oil spills, overfishing, and climate change. Predation by introduced species and human disturbance at breeding sites also pose threats to their populations.