Factors affecting breeding distribution of Storm-petrels Hydrobates pelagicus in Orkney and Shetland |
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Authors: | Ana de León Eduardo Mínguez Paul Harvey Eric Meek Jonathon E Crane Robert W Furness |
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Institution: | 1. Dipartimento di Biotecnologie e Bioscienze, Università degli Studi di Milano-Bicocca, p.zza della Scienza 2, I-20126 Milano, Italyb.sicurella@campus.unimib.it;3. Osservatorio Ornitologico Pianura Bresciana “Padernello”, via Cavour 1, I-25022 Borgo San Giacomo, Italy;4. Dipartimento di Bioscienze, Università degli Studi di Milano, via Celoria 26, I-20133 Milano, Italy;5. Dipartimento di Biotecnologie e Bioscienze, Università degli Studi di Milano-Bicocca, p.zza della Scienza 2, I-20126 Milano, Italy |
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Abstract: | Capsule The main factors are past and present human activities, especially the introduction of rats to islands. Aims To assess factors that influence breeding distribution and abundance of Storm-petrel. Methods We used a database for 142 islands in Shetland and Orkney. Breeding status of Storm-petrel was related to data for each island on introduced and indigenous predators, other human-related features, and aspects of island geography. Results Although 92% of the total land area of the archipelagos comprised islands with rats present, Storm-petrel colonies were almost totally restricted to rat-free islands. They also occurred more frequently on islands with cliffs, far from neighbouring islands with humans, and on islands with a low rate of human visits. Colony size was smaller on the smallest occupied islands. Breeding numbers of Great Skuas Stercorarius skua, Great Black-backed Gulls Larus marinus, and Storm-petrels all correlated, as each increased with island size. Conclusions The presence or absence of rats is the single most important influence on Storm-petrel breeding distribution in Orkney and Shetland. However, geographical and human-related effects, such as the presence of cliffs or the occurrence of human visits, also appear to influence the distribution of Storm-petrels, whereas avian predators appear to have had little effect until now. |
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