Berlengas Archipelago is the most important area in mainland Portugal for breeding seabirds. The archipelago hosts the only known breeding population of the vulnerable Cory’s Shearwater Calonectris diomedea borealis in mainland Portuguese coastal waters. Although this population has already been the subject of many studies, little is known about its interaction with black rat Rattus rattus. Black rat and rabbit Oryctolagus cuniculus are the only introduced mammals on the island, and the first is listed as one of the main predators of Cory’s Shearwater chicks. This study aimed to 1) evaluate the activity of black rat in two Cory’s Shearwater colonies and 2) report events of predation on chicks. For this, 54 and 20 nests were monitored daily in the colonies of Melreu and Furado Seco, respectively, between July 24 and August 6. Meanwhile, 16 photographic traps were installed within or at the entrance of 29 different nests in order to monitor rats’ activity. Despite not having obtained any record from direct predation of black rat, 2 chicks disappeared from the nest (with no photo trap) with a strong likelihood of being predated. Although in Melreu have been noticed a strong decrease in activity of black rat during development of chicks and Furado Seco not, the data presented here suggest a greater and more prolonged activity of rat at the second, which may indicate it’s under greater predatory pressure. Finnally it was found some evidences on possible impact by yellow-legged-gull on Cory’s shearwater chicks
