Seabirds breeding at the Berlengas, forty-two years after Lockley’s visit. Ibis.

The Berlengas were visited by R.M. Lockley, who stayed on the main island from 20 to 24 June 1939. At that time, only four seabird species were found breeding at Berlenga (Lockley 1952), namely Cory's Shearwater Calonectris diomedea , Shag Phalacrocorax aristotelis (c.70 pairs), Herring Gull Larus argentatus (c.1000 pairs) and Guillemot Uria aalgae (c.6000 pairs). Breeding of all four species had been known to earlier ornithologists though population sizes had not been estimated prior to Lockley's visit. Unfortunately, it is not clear which census techniques Lockley used to make his evaluation of the breeding populations (Lockley 1952), and care must be taken when using his result to check any subsequent population changes. The Berlenga islands are located off the western coast of Portugal, near the fishing village of Peniche. During the breeding seasons of 1977, 1978 and 1981, census work was carried out at the Berlengas, following current techniques described elsewhere (Cramp et al. 1974, Lloyd 1975, Nettleship 1976). A futher three species were found to breed, namely Madeiran Petrel Oceanodroma castro, Lesser Black-backed Gull L. fuscusand Kittiwake Rissa tridactyla