Alca torda britannica
Mathew describes it as a common summer resident, but less numerous than Guillemot or Puffin, and mentions the folowing breeding stations: Caldey, St Margaret's, Skokholm, Skomer, Grassholm, Ramsey and various mainland cliffs. Breeds today in suitable sites from Cemmaes Head to Caldey. Decreased during the recent war, prabably because of oil-pollution.
R.M.Lockley, G.C.S.Ingram, H.M.Salmon, 1949, The Birds of Pembrokeshire, The West Wales Field Society