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Marine Ecology Progress Series

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Northern gannet Morus bassanus female and male swap between foraging and guarding their chick on Grassholm, Wales, UK. Photo: Bethany Clark

Clark BL, Cox SL, Atkins KM, Bearhop S, Bicknell AWJ, Bodey TW, Cleasby IR, Grecian WJ, Hamer KC, Loveday BR, Miller PI, Morgan G, Morgan L, Newton J, Patrick SC, Scales KL, Sherley RB, Vigfúsdóttir F, Wakefield ED, Votier SC


Sexual segregation of gannet foraging over 11 years: movements vary but isotopic differences remain stable


Sex-specific niche differentiation is common, but we know little about how it varies over time. Clark and co-authors tested for sex differences among breeding northern gannets Morus bassanus using GPS tracking and/or stable isotopes over 11 breeding seasons. When combining GPS data from all years, females had longer foraging trips, selected different habitats and foraged at different times of day compared to males, despite broadly overlapping foraging areas. However, these differences were detected in some years but not others. Conversely, males had consistently higher red blood cell δ13C and δ15N than females across all years indicating distinct trophic niches (not linked to size dimorphism). These results highlight the importance of long-term studies and combining multiple methods.


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