Fine scale foraging behaviour of southern Buller's albatross, the only Thalassarche provisioning chicks through winter

Predators generally time their reproductive events to match the peak in prey resource availability in order to sustain the elevated energy requirement of offspring provisioning. Consequently, most temperate/polar seabirds breed in spring/summer, including the majority of small albatross species that have short breeding cycles. In contrast, the southern Buller’s albatross Thalassarche bulleri bulleri has a delayed breeding schedule, with chick-rearing extending throughout the entire austral winter. In the present study, the fine-scale at-sea movements and trophic niche of chick-rearing southern Buller’s albatross were determined at Hautere/Solander Island (New Zealand, 46° 35’ S, 166° 54’ E) during the 2016 and 2017 chick-rearing periods to investigate the winter foraging strategy used during this nominally challenging period. The tracks recorded by 15 males (n = 43) and 11 females (n = 21) revealed that foraging behaviour accounted for only a small proportion of time at sea, primarily influenced by the time of day. Foraging occurred mainly in the neritic waters of New Zealand’s South Island shelf, with individuals undertaking consistent short trips (£ 230 km from the colony) or alternating short and long trips up to 1500 km from the colony. Fine-scale tracking data revealed that males spent more time foraging, during shorter trips than females. Their isotopic niches were small, with overlap between sexes, but with males having higher dN values than females. Time spent foraging was influenced by both static and dynamic oceanographic variables. These findings suggest that southern Buller’s albatross foraging behaviour, despite having to sustain chick provisioning in winter, is similar to that of summer-breeding congeners.