Description: Territorial protandry, or early season male-biased settlement at breeding sites, is a widespread phenomenon in a range of animal breeding systems. While protandry is common across several avian lineages and has been linked with increased reproductive success of earlier breeding males in terrestrial species, the selective advantage of breeding protandry has only rarely been studied in seabirds. We assessed the seasonal changes in the sex ratio at the breeding site and sexspecific correlates of arrival date with reproductive success during 2 breeding seasons of a colonial seabird, the Australasian Gannet (Morus serrator), at Cape Kidnappers, New Zealand.We found no biases in overall sex ratios of adults and fledglings but detected a male sex bias during nest site establishment, and a significantly higher probability of reproductive success for earlier-settling males. In contrast, the reproductive success of females did not correlate with the timing of arrival. Our findings provide an assessment of the sex differences in reproductive correlates of the timing of breeding settlement in gannets and are consistent with selective advantages as suggested by indirect selection hypotheses. This study contributes to our understanding of the fitness benefits of protandry, and its linkages with sex differences in breeding philopatry and mate fidelity, in a long-lived seabird species with obligate and extended biparental care.

Description: Long-term changes in the life history and behaviour of seabirds during the non-breeding season can reflect shifts in environmental conditions. However, long-term marine studies are scarce, particularly on southern hemisphere seabirds. Here, we used moult scores from 86 Brown Skuas (Stercorarius antarcticus lonnbergi), a large predatory seabird breeding on the Chatham Islands, Aotearoa/New Zealand to model both the timing and duration of primary feather moult. In addition, we analysed stable isotope values (δ13C and δ15N) from 62 modern (2014–16) and ten museum tail feathers. These data provide insights into the non-breeding behaviour of Brown Skua. Interestingly, our results show that the primary feather moult occurred prior to birds departing the colony, starting on average on 2 January ± 5 days (SE). The average start of primary feather moult occurred five days prior to the end of breeding (7 January ± 10 days (SD)) and 42 days before the birds departed the colony (13 February ± 11 days (SD)). The average duration of primary feather moult was 189 ± 14 days (SE). Importantly, low δ13C values in four females suggested that tail feather moult might also occur while skuas are at the colony. There was no difference in tail feather δ13C and δ15N values between any pairwise comparison of modern and museum years. However, values of δ15N from tail feathers sampled in 2014 were different from those sampled in 2015 and 2016. This large annual variation in δ15N values from tail feathers over such a short period makes long-term comparisons difficult to interpret, particularly between years with low sample sizes. While the stable isotope analyses of tail feathers are informative, we recommend future studies of skuas sample the primary coverts rather than tail feathers.

Description: Urbanisation and anthropogenic alteration of ecosystems has led to conflict between humans and wildlife. Such conflict is often observed in apex predators. Although human–wildlife conflict has been extensively studied, male/female differences in behaviour are rarely considered. We investigated male/female differences in foraging behaviour of the predatory/scavenging brown skua Catharacta antarctica lonnbergi breeding on a New Zealand island nature reserve in proximity to farmland. These skuas are subject to culling, when perceived as a threat to livestock. As part of a long-term ecological study, we used high-resolution Global Positioning System (GPS) devices to characterise the space-use of foraging brown skuas. We also analysed stable isotopes of carbon (δ13C) and nitrogen (δ15N) from modern and archived blood samples to investigate possible changes in diet over the past ~30 years. Analysis of 100 GPS tracks collected from 2014 to 2016 demonstrated that males and females consistently visited different habitats. Males spent most of their time close to their breeding territory on the island nature reserve and females frequently visited a farmed island approximately two kilometres away. Consistent with this finding, we show that male and female skuas also differed markedly in their diets: males specialised on burrow-nesting white-faced storm petrels Pelagodroma marina (80%) with only a small proportion of sheep remains Ovis aries (〈6%) contributing to their diet. In contrast, female diet comprised 27% white-faced storm petrels, other seabirds (18%) and a relatively large proportion of sheep remains (47%). Further, our data (186 blood samples from 122 individuals) show that this male/female difference in diet has persisted at least since 1987. Because females fed disproportionally on sheep remains, they may be more vulnerable to being culled by farmers. Importantly, our case study suggests that intersexual differences in diet and foraging patterns can have major implications for the reproduction and survival of apex predators that interact with farming. We strongly suggest that intersexual differences in behaviour should be considered when investigating human–wildlife conflicts.