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
North Atlantic, Indian Ocean and western Pacific; in Britain and Ireland 520 pairs (450 Ireland), 80% of European total. Now seems to have stabilised after a severe decline in 1970s and 1980s.
Cornwall: now rare on passage along coasts and lower reaches of main estuaries; averages less than ten annually since 1970. Isles of Scilly: no longer breeds. Small numbers bred (up to 10% of the British and Irish population) with four-six pairs in 1993. It had been fairly stable since 1950s peaking at 12 pairs in 1959. Since 1994 there has been no proof of breeding.
Habitat & Ecology
On Scilly, it breeds only on tiny rocky islets, amongst Common Terns Sterna hirundo . The eggs are laid on rockier and higher sites than those of Common Terns.
Choice of exposed nest site on tiny islets not only invites chick predation by large gulls, but allows eggs to be washed out during stormy weather. Sites on larger
islands are known to have been destroyed by rats and cats (Robinson, 1993). European birds winter on West African coasts where trapping of Terns for food is considered to be a major reason for decline.
Provision of nest boxes on breeding islets has proved a great success, giving chicks a hiding place from marauding gulls; the only pair to have successfully reared chicks in 1993 used a box. Spreading sand onto islets helps prevent egg loss due to rolling off bare rocks (Robinson, 1993). Control of rats on uninhabited larger islands is essential. Protected under Schedule 1 of the Wildlife and Countryside Act 1981 and Annexe 1 of the European Union Conservation of Wild Birds Directive. Listed (middle 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.