Guillemots breed on rocky cliffs, using narrow ledges, and their colonies can be found around much of our coastline, including on isolated seastacks and suitable island outcrops.
Colonial breeding is the norm in this species and some colonies may number tens of thousands of individuals. Nest site locations vary between sites, with mainland sites restricted to narrow ledges safe from predators; on predator-free islands pairs may nest among rocks or even on bare ground.
During the winter months Guillemots may be encountered widely in coastal waters, though these birds are most abundant in those of the northern North Sea and off our western shores.
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Summer Auks, in breeding plumage, at the shore or near to their colonies are relatively easy to identify. But in autumn and winter we tend to see them flying rapidly past, far offshore, or bobbing around in heavy seas offering poor views. When you add to this that their distinctive breeding plumage and colouring is lost, winter Auks can be a serious challenge to identify and separate.
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During winter, Guillemots are found around much of the coast of Britain & Ireland with the highest densities in west-coast waters and the North Sea coast of southeast Scotland and northeast England. Guillemot colonies are associated with steep cliffs and rocky offshore stacks and islands, and the lack of these habitats between Flamborough Head, Yorkshire and Durlston Head, Dorset is mirrored in the breeding distribution map.
Britain and Ireland Breeding Distribution 2008-2011. More from the Atlas Mapstore.
Britain and Ireland Winter Distribution 2008-2011. More from the Atlas Mapstore.
Guillemots are recorded throughout the year though more consistently during summer at suitable coastal breeding sites.
Weekly occurrence patterns (shaded cells) and reporting rates (vertical bars) based on BirdTrack data. Reporting rates give the likelihood of encountering the species each week.
Movement
Information about movement and migration based on online bird portals (e.g. BirdTrack), Ringing schemes and tracking studies.
GUILL 
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