Patterns of activity and burrow attendance in Cory's Shearwater Calonectris diomedea as revealed by a novel logging technique

We monitored the attendance and activity of Cory's Shearwater Calonectris diomedea on Berlenga Island, Portugal, during the breeding season. To achieve this, we developed a novel logging technique to record the date and time of entrances and departures from the burrows, as well as the identity of each member of a pair. The technique enabled nonintrusive assessment of the activity of burrow-nesting animals over prolonged periods and provided very reliable information. Our study showed that males attended the nests more frequently than females during the pre-laying and chick-rearing periods. We did not find such differences during the incubation period, and both members spent similar amounts of time incubating the eggs. An index of activity (denned as number of entrances plus exits from the nest) achieved higher scores during the pre-laying and incubation periods, but the activity decreased significantly during the chick-rearing period. We did not find any effect of moonlight on the levels of activity, hour of arrival at the colony or time spent inside the burrows in breeding birds