guillemot, northern sea bird, genus Cephas, of the auk family. The black guillemot, or trystie, Cephus grylle, is about 13 in. (33 cm) long and is very striking in its breeding plumage, being entirely black from bill to tail except for large white wing patches and bright red legs. In winter its plumage is a mixture of black, white, and gray. It inhabits coasts all around the North Atlantic Ocean, but is more abundant on the American side, where it is found as far south as Cape Cod. The pigeon guillemot, C. columba, is very similar to the black guillemot, and may be a geographic variety rather than a distinct species. It is found on Pacific coasts from the Bering Sea to S California and N Japan. Guillemots are distinctive among auks in a number of ways: they are better fliers than most, they are not very gregarious, and the female lays two or three eggs at a time instead of the usual one. Pairs of guillemots tend to occupy particular territories in the water, where they swim and dive for food. Like other auks, they build no nest, but lay their eggs on the rocks. In Great Britain a related bird, called murre in North America, is also called guillemot. Guillemots are classified in the phylum Chordata, subphylum Vertebrata, class Aves, order Charadriiformes, family Alcidae.

Guillemot is the common name for several species of seabird in the auk family, comprising two genera: Uria and Cepphus. This word of French origin apparently derives from a form of the name William, cf. the Gwillim or the Guillaume.

The Uria are known as murres in North America and, together with the Razorbill, Dovekie and the extinct Great Auk, make up the tribe Alcini. They have distinctly white bellies, thicker, longer bills than Cepphus and form very dense colonies on cliffs during the reproductive season.

The three species of Cepphus - for which the term "guillemot" is generally reserved in North America - form a tribe of their own: Cepphini. They are smaller than the Uria species, have black bellies, rounder heads and bright red feet.



Some prehistoric species are also known:

  • Uria bordkorbi (Monterey or Sisquoc Late Miocene of Lompoc, USA)
  • Uria affinis (Late Pleistocene of E USA) - possibly a subspecies of U. lomvia
  • Uria paleohesperis

U. brodkorbi is interesting insofar as it is the only known occurrence of the Alcini tribe in the temperate to subtropical Pacific, except for the very fringe of the range of U. aalge. It suggests that the Uria species, which are the sister taxon to all the other Alcini, and like them are usually believed to have evolved in the Atlantic, may have evolved in the Caribbean or possibly close to the Isthmus of Panama. The modern Pacific distribution would then be part of a later arctic expansion, whereas most other auk lineages form clades with a continuous range in the Pacific, from Arctic to subtropical waters.


As in other genera of auks, fossils of prehistoric forms of Cepphus have been found:

  • Cepphus olsoni (San Luis Rey River Late Miocene - Early Pliocene of W USA)
  • Cepphus cf. columba (Lawrence Canyon Early Pliocene of W USA)
  • Cepphus cf. grylle (San Diego Late Pliocene, W USA)

The latter two resemble the extant species, but because of the considerable distance in time or space from their current occurrence, they may represent distinct species.


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