Long and Short Trips in Nonbreeding Buller's Albatrosses: Relationships with Colony Attendance and Body Mass

Abstract

Abstract Foraging strategies of nonbreeding seabirds attending colonies remain virtually unknown. Here we report the results of a satellite telemetry study of nonbreeding Buller's Albatrosses (Thalassarche bulleri) from the Snares island group south of New Zealand in 2000–2001. Two 6- to 7-year-old prebreeding birds dispersed to Tasmania, Australia, from late May until at least late July. Six older birds (five prebreeding birds, one former breeding adult) all adopted a dual strategy of short trips (mean duration 1.3 days, mean foraging range 129 km) and long trips to southern New Zealand (9.6 days, 871 km) or Tasmania (22.0 days, 1918 km). Time allocation to short trips increased with age and experience (both sexes) and nest-site attendance (males), and decreased during the guard (when the chick is attended) and late postguard (chick left unattended) stages (females). Up to the guard stage, most birds present at their colony on consecutive days foraged overnight (mean foraging range 101 km). Nonbreeding birds used the same foraging areas as breeding adults, but allocated more foraging time to short trips during the corresponding incubation period and early postguard stage, and to long trips during the guard stage. Results suggest that prebreeding birds explore foraging areas sequentially, and increase their time ashore by progressing from making only long trips, to introducing short overnight trips, to modifying the duration of and allocation between long and short trips. Changes in body mass recorded on Solander Island (160 km north of the Snares) show that experienced nonbreeding birds initiate long foraging trips to regain mass lost during short trips, and suggest that less frequent short trips (and hence fewer returns ashore) among inexperienced birds are related to less efficient foraging during long trips.