The Status and distribution of European Storm-petrels Hydrobates pelagicus and Manx Shearwaters Puffinus puffinus on the Isles of Scilly

This paper describes the first comprehensive survey of the distribution and abundance of breeding European Stormpetrels and Manx Shearwaters on the Isles of Scilly. Diurnal tape playback of vocalisations was used to survey those islands in the archipelago on which birds had previously been reported breeding and to search others with suitable habitat. The total breeding population of Storm-petrels was 1475 Apparently Occupied Sites and of Manx Sheanvaters 201 Apparently Occupied Burrows. These numbers are of regional importance for both species and the numbers of Storm-petrels are internationally important. Storm-petrel breeding distribution was restricted to rat-free outer islands, but some Manx Shearwater colonies were found on islands with rats and also feral cats. The role of eradication and control of mammalian predators in the conservation of petrels on the Scilly Isles is discussed.