The Great Shearwater is nearly as large as Cory's Shearwater, but flies with stiffer, more rapid wingbeats a bit like a Fulmar. Its dark brownish grey cap contrasts with its white collar which may extend all the way round the back of the nape, and it has dark markings on its underwings and belly where Cory's is pretty much all white. Its bill is narrow and dark. It breeds on islands in the south Atlantic, then winters on the sea in the north Atlantic east of North America (during the Northern Hemisphere's summer). Its southward migration takes a more easterly route, and it is during this time that it can show up in western European waters, sometimes off the southwest coast of the UK.