FORAGING STRATEGY OF WANDERING ALBATROSSES THROUGH THE BREEDING-SEASON - A STUDY USING SATELLITE TELEMETRY

Satellite telemetry of Wandering Albatrosses (Diomedea exulans) breedi ng on the Crozet Islands, southwestern Indian Ocean, revealed two dist inct foraging strategies during successive stages of the breeding seas on: systematic foraging over extensive distances; and use of specific areas close to the colony. During early incubation, Wandering Albatros ses foraged over pelagic waters at an average range of 1,284 km. The l ength of the foraging trips decreased towards the end of the incubatio n period. During the first month of chick rearing when parents brood a lternately for short periods, the foraging range, distance covered, an d area prospected were further reduced. Males tended to return to an i ndividual foraging area, located at the edge of the continental shelf, that had previously been visited during the long trips of the incubat ion period. Females mostly prospected pelagic waters just off the shel f. After the chick had been left alone on the nest, birds exhibited a two-fold strategy, combining long foraging trips over pelagic waters w ith short trips over the shelf. Generally, both sexes headed for and f oraged over an extensive pelagic sector. Some males also foraged over the Kerguelen shelf. Females tended to forage over more northerly wate rs than males. The duration of the foraging trips was most closely rel ated to the total distance covered, but also to the maximum range duri ng the long trips of the chick-rearing period and to a lesser extent d uring the incubation period. There were no such significant relationsh ips in the case of short trips. During long pelagic foraging trips, th e birds had a looping course that was determined by the wind direction , suggesting random foraging with respect to prey distribution. We wer e able to show that Wandering Albatrosses use two foraging strategies to cope with the constraints imposed by the different stages of the br eeding cycle, the availability of prey, and the distribution of the pr ey. Use by Wandering Albatrosses of two foraging strategies may be a c ompromise based on the simultaneous need to satisfy the different food requirements of chicks and parents.