“…Differences in energetic demands over the breeding season may also lead to variation in body condition (Moe et al, 2002) but all individuals in this study were sampled during the chick provisioning period. Sex-linked differences in scaled mass have been observed previously in Northern gannets and may reflect the differing physiological demands of reproduction, and breeding role specialization, as well as more subtle differences between the sexes in prey-capture techniques, nutritional requirements and fine-scale habitat and prey selection (Stauss et al, 2012;Cleasby et al, 2015;Machovsky-Capuska et al, 2016;Bodey et al, 2018b). The difference in scaled mass between individuals at Grassholm and Bass Rock may reflect variation in the prey resources and environmental conditions accessible to individuals from their respective colonies.…”