Impact of predation by the Black Rat Rattus rattus on the breeding success of Cory’s Shearwater Calonectris diomedea on Linosa island (Sicily, Italy)

We studied the impact of predation by the Black Rat on the breeding success of Cory’s Shearwaters on Linosa island (Pelagian archipelago) in 2006. Between 6 and 10 June we marked 231 active nests, which we checked in July, September and October. In July we found eggs or pulli in only 121 nests, while in the remaining 110 we found: 4 abandoned eggs, 1 crushed egg, 80 predated eggs, and 23 predated chicks; in two cases adults were present without eggs or chicks. In September we found 91 eggs or chicks, while 30 were predated by rats. In October no rat predation was observed. The reproductive success was 39%, rat predation being 59% and natural losses 2%, but long-term studies are needed to better quantify the exact effects of rat predation on Linosa’s shearwater population.