Stable isotopes reveal the importance of seabirds and marine foods in the diet of St Kilda field mice

Bicknell, A. W.J., Walker, B. W., Black, T., Newton, J. , Pemberton, J. M., Luxmoore, R., Inger, R. and Votier, S. C. (2020) Stable isotopes reveal the importance of seabirds and marine foods in the diet of St Kilda field mice. Scientific Reports, 10, 6088. (doi: 10.1038/s41598-020-62672-x) (PMID:32269251) (PMCID:PMC7142145)

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Abstract

Introduced mammals have devastated island nesting seabird populations worldwide. Declines in breeding seabirds on St Kilda, UK, have been linked to climate change and predation from great skuas Stercorarius skuas, but the introduced St Kilda field mouse Apodemus sylvaticus hirtensis may also play a role by feeding on adults, chicks or eggs. Here, we use stable isotopes in St Kilda mouse blood and potential dietary items to investigate their foraging ecology, specifically focussing on the importance of seabirds and marine foods in their diet. Mice were seasonally sampled at three sites on Hirta, St Kilda over three consecutive years (2010–2012). The δ13C and δ15N ratios were used in analyses, including isotope niche and dietary source mixing models, to examine foraging behaviour among locations and between seabird breeding seasons. Mice sampled in Carn Mor – where the majority of the island’s seabirds nest - had consistently higher δ13C than other locations throughout the year, with δ15N also being significantly higher for all but one comparison. The isotopic niche width (SEAs) of Carn Mor mice in each season were distinct from the other locations, and became smaller during the seabird breeding season. Dietary mixing models revealed that seabirds made up a large proportion of the diet for mice from Carn Mor, particularly during the seabird breeding season. In conclusion, our work reveals that seabird-derived foods are likely to form a significant part of the diet of St Kilda mice populations located in and around breeding colonies. It is unclear however, whether this is from scavenging or predation of seabirds, or through their discarded food items. Given that mice have had significant effects on seabird populations elsewhere, it is important to carry out further work to determine whether mice are a significant cause of seabird mortality in this island ecosystem.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Newton, Dr Jason
Creator Roles:
Newton, J.Formal analysis, Writing – review and editing
Authors: Bicknell, A. W.J., Walker, B. W., Black, T., Newton, J., Pemberton, J. M., Luxmoore, R., Inger, R., and Votier, S. C.
College/School:College of Science and Engineering > Scottish Universities Environmental Research Centre
Journal Name:Scientific Reports
Publisher:Springer Science and Business Media LLC
ISSN:2045-2322
ISSN (Online):2045-2322
Copyright Holders:Copyright © The Author(s) 2020
First Published:First published in Scientific Reports 10:6088
Publisher Policy:Reproduced under a Creative Commons Licence

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