THE STATUS AND DISTRIBUTION OF THE RED-THROATED DIVER GAVIA-STELLATA IN BRITAIN IN 1994

The first national survey of breeding Red-throated Divers Gavia stella ta in Britain teas carried out in 1994. It was based on two visits to all standing freshwater in Shetland and Orkney, and to a sample elsewh ere in the species' range in Scotland (Inner and Outer Hebrides and ma inland). The survey located an estimated 855 breeding pairs (95% CI 73 5-990) and 1295 (95% CI 1075-1525) non-breeding adults. About 12% of b irds that were recorded as non-breeding probably bred, but were not pr oved to do so; taking these into account the corrected total populatio n for Scotland was estimated at 935 breeding pairs, with approximately 430 (46%) of these in Shetland, 105 (11%) in Orkney and 400 (43%) els ewhere in Scotland. In fetal, there were an estimated 3010 (95% CI 268 5-3360) adult Red-throated Divers in Scotland during summer 1994. The Red-throated Diver population in Shetland has declined by more than a third since 1983, that in Orkney is probably stable and trends elsewhe re are unknown. A comparison with Red-throated Diver populations on th e Northern Isles showed that on the mainland densities were very much lower that a smaller proportion of the birds present bred, that they d id so on much larger lochs and that when they did breed they were less successful. In Shetland, breeding pairs on small lochs were more succ essful than those on large lochs; some potential reasons for this are discussed.