The coasts of the Bay of Biscay and the western Iberian Peninsula are used by several seabird species for breeding. These include the European storm petrel Hydrobates pelagicus, European shag Phalacrocorax aristotelis, yellow-legged gull Larus michahellis, lesser black-backed gull Larus fuscus, black-legged kittiwake Rissa tridactyla, and common guillemot. Many more species use these waters for feeding in the non-breeding period. The most important species in terms of abundance are northern gannet Morus bassanus, gulls Larus spp. (seven species), Balearic shearwater Puffinus mauretanicus, Manx shearwater Puffinus puffinus, sooty shearwater Puffinus griseus, Cory’s shearwater Calonectris diomedea, razorbill Alca torda, and Atlantic puffin Fratercula arctica. Trends in the numbers of seabirds breeding around these seas are not known, with the exception of Iberian common guillemot and black-legged kittiwake that are either now extirpated or close to that state. Shags have also declined.