Status and distribution of breeding Common Scoters Melanitta nigra nigra in Britain and Ireland in 1995

Abstract

The status and distribution of Common Scoters Melanitta nigra nigra in Britain and Ireland were determined from a survey in April–June 1995. Three visits were made to all known, and a sample of potential, breeding sites. A total of 439 birds was located, from which the British and Irish population was estimated at 195 pairs (100 in Ireland, 95 in Britain). In Ireland, three sites held 100 pairs or 51% of the population. In Britain, birds were spread over 61 sites in 23 10-km squares, all in Scotland. Breeding Common Scoters are somewhat more abundant in Britain and Ireland than hitherto thought. However, this is due mainly to comprehensive survey coverage in 1995 and, over the past 30 years, Common Scoters have actually suffered both population decline and range contraction. The Irish population declined from 180 to 100 pairs between 1967 and 1981, but has since remained stable. In Britain, Common Scoters have ceased to breed on Shetland, in Central Scotland, and in Dumfries & Galloway. Historical data are lacking, but in the Flow Country numbers have declined from some 50 pairs in 1988 to 35 pairs in 1995. All birds in Ireland, but only half of those in Britain were on protected sites. Given the Common Scoter's threatened status in Britain and Ireland and since the population dynamics of the species are largely unknown, annual monitoring of numbers and productivity is required to determine population trends and establish natural limits of population fluctuation. As Common Scoters in Britain and Ireland are threatened both by factors operating over whole water catchments (deteriorating water quality resulting from eutrophication and afforestation) and at individual sites (competition with introduced Roach, predation by American Mink), integrated catchment management plans, including site safeguard measures, seem necessary for the effective conservation of the species.