Foraging strategies of breeding seabirds studied by bird-borne data loggers

Our research group has devised and manufactured a data logger which glued on the back of a bird, can detect and memorise the direction in which the bird is heading during a flight. Given the birds' constant cruising speed, the memorised data can be used to recon-struct the whole flight path. Subsequent versions of this direction recorder, equipped with new sensors (depth meter and flight sensor), were used to investigate the foraging behaviour of several species of breeding marine birds (Balearic shearwater, Brünnich's guillemot, com-mon guillemot, razorbill, black-legged kittiwake, Audouin's gull, northern gannet, blue-foot-ed booby). The data recorded at different colony sites allowed us to identify the birds' feed-ing grounds and record the most relevant events occurring in the foraging trips, including the duration of the trips, total flight time, number and duration of the stops where feeding actual-ly occurred, dive profiles and diving behaviour. Differences in the foraging strategies between sexes and between incubating and brooding birds were also investigated.