Two colonies of H. p. melitensis were studied in the Benidorm Island during 1993. More than 400 pairs were estimated on the island. The first clutches were laid in the second half of April and the last eggs were laid in the first week of July. In both colonies most eggs (76.2% and 75.0%) were laid during May. Nesting success, estimated by the Mayfield-40% method, was markedly smaller in one colony (7.12%) than in the other (61.78%), but the mean apparent overall breeding success in Benidorm, 0.63 flying chicks per nest, was higher than in the Atlantic colonies. Breeding success may have been affected by nest-site related factors and predation by Yellow-legged Gulls (Larus cachinnans).