At least 19 species of seabird breed on the coasts of the Greater North Sea, in particular large numbers of northern gannet Morus bassanus, herring gull Larus argentatus, lesser black-backed gull Larus fuscus, black-legged kittiwake Rissa tridactyla, and common guillemot Uria aalge.
Broadly, the numbers of breeding seabirds increased until about 2000, after which there was a decline. The North Sea is used for feeding, both by breeding species on its coasts and by birds from further afield during the non-breeding season. Immigrants during winter from the north and east are of particular note. Numbers of some of these immigrants have been declining, possibly due to milder winters, meaning that these migrants can remain in waters closer to their breeding grounds.
Threatened and declining seabird species in the Greater North Sea ecosystem according to OSPAR:
Puffinus mauretanicus Balearic shearwater
Rissa tridactyla Black-legged kittiwake
Sterna dougallii Roseate tern
