Puffinus puffinus puffinus
Mathew called Skomer "the largest breeding-station . . .in the British Isles," which may be correct. He believed that a few might nest on Ramsey; the Modern Universal British Traveller, 1779, states that the "Harry-bird" (ie the Shearwater, see Oxford Dictionary 1901) breeds at Ramsey, and there is a good description of it nesting in holes there. Mathew gives some evidence that they were possibly breeding on St Margaret's Island in 1893, and perhaps also on Caldey; he seems not to have known of the Skokholm colony. About 25,000 pairs breed on Skomer, and at least 10,000 pairs on Skokholm. Visits the whole coast at night, from March to August, and often heard calling inland (eg Haverfordwest)
R.M.Lockley, G.C.S.Ingram, H.M.Salmon, 1949, The Birds of Pembrokeshire, The West Wales Field Society