information on the biology of species and the ecology of habitats found around the coasts and seas of the British Isles

Common guillemot (Uria aalge)

Distribution data supplied by the Ocean Biogeographic Information System (OBIS). To interrogate UK data visit the NBN Atlas.



The common guillemot is a rather dumpy, thick set auk reaching a maximum size of about 46 cm, and with a wingspan up to 73 cm. The breeding plumage has dark chocolate brown upperparts and head to the lower throat, and white underparts with some dark streaking on the flanks. Between different populations there is variation in the extent of this streaking. During the winter the sides of the face and throat are white. However, the extent of this colouration also varies between populations. The bill is long, slender and pointed, and the feet are black. A 'bridled' form occurs with a white eye ring and white stripes behind the eye. Juveniles resemble adults but display a variable amount of white on the throat.

Recorded distribution in Britain and Ireland

Breeding pairs are more commonly found in Scotland, but are found all around British and Irish coasts.

Global distribution



Uria aalge spends most of its life at sea, normally coming ashore only to nest for the May breeding season, but may return to colonies as early as September. Nests are made on bare, narrow ledges on steep cliffs, often in large numbers. Guillemots disperse widely during the winter but may be seen offshore around the UK.

Depth range


Identifying features

  • Upperparts and head to lower throat of breeding plumage are a dark chocolate brown.
  • Underparts are white.
  • Sides of head and throat are white in winter.
  • Long, slender, pointed black bill.

Additional information

The diet consists mainly of fish but may include crustaceans. Please note that distribution maps are compiled using records for both breeding and wintering populations. For more specific distribution and abundance records please refer to maps compiled by The British Trust for Ornithology, available at

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    This review can be cited as:

    Sweet, N. A. 2008. Uria aalge Common guillemot. In Tyler-Walters H. and Hiscock K. (eds) Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 25-09-2018]. Available from:

    Last Updated: 23/09/2008