Year-round distribution and habitat preferences of the Bugio petrel

The conservation of threatened seabirds that are highly pelagic, such as the gadfly petrels Pterodroma spp., depends on understanding the main oceanographic determinants of their movements in order to apply the necessary management regulations and to identify and protect their key marine habitats. The present work presents for the first time information on the distribution and habitat preferences of 17 Bugio petrels Pterodroma deserta from the island of Bugio, Madeira archipelago, North Atlantic Ocean. All of the birds remained in North Atlantic waters during the pre-laying exodus, incubation and chick-rearing periods, showing a clear preference for deep, productive (high chlorophyll a levels) waters north of the Azores archipelago. There was high individual variability in migration strategies. Five wintering areas were identified: two off the Brazilian coast, one around the Cape Verde archipelago, one off the southeast coast of the United States, and one in pelagic waters in the central South Atlantic. These tended to be areas of high productivity but not of a particular sea surface temperature regime. Based on saltwater immersion data, birds were more active during the breeding season and spent more time resting on the water in wintering areas. There was also a positive correlation between the time spent on the water and the progression of full to new moon, suggesting that the birds may use moonlight to search for prey. Given its highly dispersed distribution at sea throughout the year, effective conservation of this threatened species may require management at large spatial scales.