The descriptive text, below the map, is from the Cornish Red Data Book (2009). The map on this web page depicts the organisms distribution and shows the records made pre-2000 and those made since.
Range & Status
Holarctic; in Britain and Ireland 13,000 breeding pairs (40% of European population), slowly increasing.
Cornwall: passage migrant in moderate numbers along coasts and lower reaches of main estuaries, most important staging areas being lower reaches of the Tamar and Camel, St. Ives Bay and Mount' s Bay. One pair bred in 1998, but no evidence of any subsequent breeding. Isles of Scilly: bred up to 1905 (chiefly Annet); bred again 1978 and most subsequent years in variable numbers, e.g. 20 pairs 1987, three in 1993 (unsuccessful). Since then breeding has become sporadic with none successful.
Habitat & Ecology
Colonies are known to fluctuate from year to year, with much interchange; most successful colonies are mixed with those of Black-headed Gulls Larus ridibundus (which do not breed on Scilly). On Scilly, it forms mixed colonies with breeding Common Terns Sterna hirundo and breeds on low islets and upper reaches of beaches. Scilly birds winter along coastal waters of north and west Africa.
Predation by rats is a serious hindrance to sustained re-colonisation of Scilly. Rat predation created a complete breeding failure from the 15 pairs that nested amongst Common Terns on Samson in 1991 (Robinson, 1993).
In 1992 rats were almost completely eliminated from Samson; continuation of the rat control programme is essential. Protected under Annexe 1 of the European Union Conservation of Wild Birds Directive. Listed (long list) as a globally threatened/declining species (BSGR, 1995).
I.J. Bennallick, S. Board, C.N. French, P.A. Gainey, C. Neil, R. Parslow, A. Spalding and P.E. Tompsett. eds. 2009. Red Data Book for Cornwall and the Isles of Scilly. 2nd Edition.Croceago Press.
The Cornish Red Data Book Project was led by the Cornwall and Isles of Scilly Federation for Biological Recorders (CISFBR). The full text and species accounts (minus the maps) are available on the CISFBR website.