Uria – Murres

The robust and hardy birds are efficient swimmers and divers, spending most of their lives in the water

Uria comprises species such as murres in North America, guillemots in the UK, and turrs in Newfoundland, consisting of medium-sized seabirds that are members of the auk family, Alcidae. These birds are highly adapted to marine life, spending most of their time at sea, and they are known for their distinctive black and white plumage and their proficiency in diving.

Uria species, specifically the common murre or guillemot (Uria aalge) and the thick-billed murre (Uria lomvia), are often mistaken for penguins when on land due to their upright posture and similar coloration. However, unlike penguins, murres are excellent fliers with slender, pointed wings that enable them to ‘fly’ underwater as they pursue their prey.

Their heavy-bodied appearance belies their agility in the water. They have evolved to have a high muscle-to-fat ratio with a strong, streamlined body that makes them efficient swimmers, capable of reaching depths of over 100 meters as they hunt for fish and squid. Their black or brown upperparts and white underparts provide camouflage from predators; when viewed from above, they blend with the dark depths, and from below, they merge with the light surface.

The differences between the common murre and the thick-billed murre are subtle yet significant. The common murre tends to have a brownish-black back and a more slender and pointed bill, whereas the thick-billed murre possesses a stockier bill and often a blacker back. This differentiation in bill shape and size is related to their feeding habits and the type of prey they target.

Murres are known for their remarkable breeding colonies, which are among the densest of any bird species. They typically breed on steep cliff faces and rocky outcrops along the coasts of the North Atlantic and North Pacific Oceans, where they return annually to the same breeding sites. The ‘bridle’ marking, a white eyering connected to a white line extending back from the eye, is a breeding plumage feature that is particularly evident in the bridled form of the common murre.