Population decline of Leach’s Storm-petrel Oceanodroma leucorhoa within the largest colony in Britain and Ireland

Abstract

This study used diurnal playback of vocalisations to examine the abundance of breeding Leach’s Storm-petrel Oceanodroma leucorhoa on Dun, St Kilda in 2003 and 2006 in relation to the only previous survey conducted using similar methodology in 1999. The number of Apparently Occupied Sites in 2006 was 12,770, not significantly different to the 14,490 found in 2003, but significantly lower than the 27,811 found in 1999, by 54%. The magnitude and rate of the decline are of major conservation concern. Great Skua Stercorarius skua predation is thought the most likely cause but other factors such as poor food supply cannot be ruled out. The importance of continued monitoring of Leach’s Storm-petrel and Great Skua is discussed.