Radio-telemetry as a tool to define protected areas for seabirds in the marine environment

Although most Manx shearwaters (Puffinus puffinus) in the UK are protected within Special Protection Areas (SPAs) at their breeding colonies, such site-based protection does not currently extend into the marine environment. Manx shearwaters form rafts (dense flocks of birds) on the sea adjacent to their breeding colony from late afternoon onwards, before coming ashore after nightfall. The ecological and protection requirements of Manx shearwaters in the UK would be more completely addressed if existing SPA boundaries were extended into adjacent marine areas to include those used for rafting behaviour. However the spatial extent of rafts has never been assessed accurately. Because rafting behaviour continues after nightfall, radio-telemetry was used to investigate rafting distributions of Manx shearwaters around the three largest UK colonies: Skomer (south-west Wales), Bardsey (north-west Wales) and Rum (north-west Scotland). Totals of 30, 28 and 30 birds were radio-tagged, with 174, 264 and 385 rafting locations estimated for Skomer, Rum and Bardsey, respectively. Kernel contour analysis was used to describe the ‘rafting range’ around each colony. The maximum extent of the 95% kernel contours was used to determine the area which would encompass most rafting birds. The maximum extents of rafting ranges were 4, 6 and 9 km, respectively for Skomer, Rum and Bardsey. We believe this is the first successful illustration of how radio-telemetry data can potentially be used to define protected areas for birds in the marine environment.