Typically a species of northern and western coasts, the largest colony in Scotland is at Mingulay and Berneray with some 10% of the EU population.
Other large colonies are to be found at Fair Isle, Caithness and Handa Island. While normally nesting in crevices scattered amongst other seabirds, a single cliff face at the west end of Berneray is home to almost 5000 pairs. Predation by brown rats (at Canna) and American Mink at other sites is known to have reduced numbers.
Food: Dives normally to 2-3 m but can dive deeper. Chiefly fish (sand eels) with some invertebrates. Submersion not more than 22 s (maximum 40-52 s).
Nest Site: Rock ledges and crevices beneath rock overhang; sometimes uses old rabbit or puffin burrow.
Breeding: Mid April to mid June where 1 egg is laid and very rarely 2.
Wintering: Northern populations are mainly migratory. Scottish population south west Norway where they feed and moult, Bay of Biscay, Morocco and western Mediterranean.
Distribution: Mainly west coast of the UK, Southern Ireland, Iceland, Faeroes, Bear Island, Jan Mayen, France, Norway, Sweden, Finland, Russia.