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

Bethany L Clark; Sam L Cox; Kelly M Atkins; Stuart Bearhop; Anthony W J Bicknell; Thomas W Bodey; Ian R Cleasby; W James Grecian; Keith C Hamer; Benjamin R Loveday; Peter I Miller; Greg Morgan; Lisa Morgan; Jason Newton; Samantha C Patrick; Kylie L Scales; Richard B Sherley; Freydís Vigfúsdóttir; Ewan D Wakefield; Stephen C Votier

doi:10.3354/meps13636

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

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

Bethany L Clark, Sam L Cox, Kelly M Atkins, Stuart Bearhop, Anthony W J Bicknell, Thomas W Bodey, Ian R Cleasby, W James Grecian, Keith C Hamer, Benjamin R Loveday, …

Marine Ecology - Progress Series, Vol.661, pp.1-16

2021

DOI: https://doi.org/10.3354/meps13636

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Abstract

sex-specific

ecological niche

stable isotopes

biologging

seabird

central-place foraging

Northern gannet

Morus bassanus

Sex-specific niche differentiation is common in marine vertebrates, but how this varies long-term is poorly understood. Here we investigated interannual variation in sexual segregation among breeding northern gannets Morus bassanus, wide-ranging central-place foragers with slight sexual dimorphism. Over 11 breeding seasons, we used GPS tracking and/or stable isotopes to test for sex differences in foraging trip characteristics (range, duration and timing); spatial distribution; habitat selection; and carbon and nitrogen isotopes in blood. When combining data from all years, females foraged further and for longer than males, yet despite this, the foraging areas of the sexes almost completely overlapped. Males and females selected foraging habitats that differed in terms of oceanography but not fishing vessel density. We also detected temporal segregation: females were more likely to be at sea during the day than at night, while males were more likely to be at sea during the night. However, foraging behaviour quantified by all GPS analyses varied interannually, with sex differences detected in some years but not others. Finally, males had consistently higher red blood cell δ13C and δ15N than females across all years, which was not driven by size dimorphism, instead likely by prey choice or very fine-scale habitat selection. We conclude that environmental variation influenced short-term sex differences in movement, but sex differences in stable isotopes that integrate behaviour over longer periods reveal more consistent differences. Our results suggest that inferences drawn from single-year studies may not relate to general patterns, highlighting the importance of long-term studies and combining methods.

Details

Title: Sexual segregation of gannet foraging over 11 years: movements vary but isotopic differences remain stable
Authors: Bethany L Clark (Author) - University of Exeter
Sam L Cox (Author) - La Rochelle Université
Kelly M Atkins (Author) - University of Exeter
Stuart Bearhop (Author) - University of Exeter
Anthony W J Bicknell (Author) - University of Exeter
Thomas W Bodey (Author) - University of Exeter
Ian R Cleasby (Author) - Royal Society for the Protection of Birds
W James Grecian (Author) - University of St Andrews
Keith C Hamer (Author) - University of Leeds
Benjamin R Loveday (Author) - Plymouth Marine Laboratory
Peter I Miller (Author) - Plymouth Marine Laboratory
Greg Morgan (Author) - Royal Society for the Protection of Birds
Lisa Morgan (Author)
Jason Newton (Author) - Scottish Universities Environmental Research Centre
Samantha C Patrick (Author) - University of Liverpool
Kylie L Scales (Author) - University of the Sunshine Coast, Queensland, School of Science, Technology and Engineering
Richard B Sherley (Author) - University of Exeter
Freydís Vigfúsdóttir (Author) - University of Iceland
Ewan D Wakefield (Author) - University of Glasgow
Stephen C Votier (Author) - University of Exeter
Publication details: Marine Ecology - Progress Series, Vol.661, pp.1-16
Publisher: Inter-Research
Date published: 2021
DOI: 10.3354/meps13636
ISSN: 1616-1599; 0171-8630
Copyright note: © The authors 2021. Open Access under Creative Commons by Attribution Licence. Use, distribution and reproduction are unrestricted. Authors and original publication must be credited.
Organisation Unit: University of the Sunshine Coast, Queensland; School of Science, Technology and Engineering
Language: English
Record Identifier: 99553504802621
Output Type: Journal article