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
W. Palearctic; in Britain and Ireland 543,000 pairs in 1985/87.
Cornwall: a marked decrease in the breeding population; the most recent survey (Seabird 2000) recorded 1956 occupied nest sites in June 2000, a decrease of some 30% on the 1987 survey which had recorded at least 2800 nests. Isles of Scilly: although bred in the early 19th century, did not breed again on the islands until 1938, increasing to 1400 pairs by 1969/70. Subsequent decline to some 300 pairs through the 1990s, to 250 by 2001. In 2007 no young were reared to fledging on Scilly and very few from Cornish mainland colonies.
Habitat & Ecology
A pelagic gull, generally feeding offshore, only visiting coastal cliffs to nest. Long increase in 1950s and 1960s attributed to the development of the fishing industry, but dramatic decrease since 1990 presumed due to overfishing of sand-eels, an important food source for the young. In some years virtually no young are reared to fledging due to lack of food resources.
Rock climbing and low-flying aircraft can both cause considerable chick or egg loss when panic created by sudden noise forces adults into the air. Overfishing of sand-eels. As we are at the southernmost limit of the breeding range, then global warming and a general rise in sea temperatures might be having some effect.
Monitoring of breeding colonies.
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.