Habitat
Arctic Tundra. In Britain off rocky coasts and in sheltered bays and estuaries. During the breeding season on freshwater pools, small lakes and slow-moving rivers.
Canada (B) (NB) (P), Denmark (NB) (P), Finland (NB), Greenland (B) (NB), Iceland (NB), Japan, Norway (NB), Russia (Asian) (B), Russia (Central Asian) (B), Russia (European) (B) (NB) (P), St Pierre and Miquelon (NB) (P), Svalbard and Jan Mayen Islands (B), Sweden (NB), USA (B).
Vagrant to Belgium, Czech Republic, France, Germany, Hungary, Ireland, Italy, Kazakhstan, Latvia, Lithuania, Netherlands Antilles, Poland, Portugal, Spain, United Kingdom.
Arctic coasts, except Iceland and Scandinavia, where may breed sporadically.
 
Population
Estimated population is 790,000 - 930,000 (2010).
The Reader's Digest Book of British Birds 1980, 3rd Edition, Drive Publications Ltd ISBN 0 340 25308 8
Birds in Colour Campbell, B., 1960, Penguin Books Ltd
The Pocket Guide to Nest and Eggs Fitter, R.S.R., 1954, Collins
RSPB Handbook of British Birds Holden, P., Cleeves, T., 2002, A & C Black ISBN 0 7136 5713 8
Birds of Britain and Europe Sterry, P., et al., 2001, AA Publishing ISBN 0 7495 3068 5
The Popular Handbook of British Birds Hollom, P.A.D., 1973, H.F. & G. Witherby Ltd ISBN 0 85493 002 7