Sex differences in individual foraging site fidelity of Campbell albatross

Abstract

Inter-individual variation in behavioural traits has important implications for evolutionary and ecological processes. Site fidelity, where individuals consistently use the same foraging site, is common among marine predators. Sex differences in foraging are also well studied in marine vertebrates, but the extent to which consistent inter-individual differences in foraging vary between the sexes is poorly known. Here we quantified the effects of sex on individual foraging site fidelity (IFSF), both within and between years, in chick-brooding Campbell albatross Thalassarche impavida. Using bird-borne global positioning system loggers, we calculated route fidelity (nearest-neighbour distance), repeatability of site fidelity (terminal latitude and longitude), and foraging effort (total distance travelled and trip duration) during 2 to 10 repeat trips. Overall, Campbell albatrosses showed a high degree of site fidelity. Birds travelled to similar sites not only within the same year, but also between 2 consecutive years, suggesting that the within-year consistency is not simply in response to short-term patches of food. Moreover, within the same year, we found differences in terms of IFSF between the sexes. Females that foraged closer to the colony in neritic and shelf waters were more likely to follow similar routes on repeated foraging trips and were more consistent in their foraging effort than males. Males that foraged further offshore in pelagic waters had more repeatable foraging longitudes than females. Our study provides further evidence of the importance of IFSF among marine vertebrates. However, it also reveals that the strength of such specialisations may vary with sex.