Status of the Balearic shearwater (Puffinus mauretanicus) on the Galician coast (NW Iberian Peninsula

Abstract

This paper aims to assess the status of the threatened Balearic shearwater Puffinus mauretanicus along the Galician coast (NW Iberian Peninsula) by studying its movements and numbers. Balearic shearwaters are detected off Galicia during their annual cycle although they are uncommon between November and May. Overall, 44 groups of over 150 birds have been recorded in seven main areas since 1976, especially in the Vigo Ria and the Pontevedra Ria and along the coast of Bergantiños (Sisargas-Baldaio). Birds have been observed moulting primary and secondary feathers, mainly in June. North-eastward migration is evident along the Atlantic coast (capes Silleiro and Fisterra, daily maximum of 476 birds per hour) between June and August, where it seems to overlap with local movement. However, south-westward migration is far more frequent between September and October (daily maximum of 360 birds per hour) along the Cantabrian coast. The results might be biased due to the methodological problems, on account of the existence of irregular flows, an important inter-annual variability and local movements, probably brought about by the distribution of food resources.