Abstract
Several studies have attempted to identify the selective pressures leading to reversed size dimorphism (RSD), a characteristic of skuas and of a wide range of bird species with a raptorial lifestyle. One of the prevailing hypotheses posits that females in species of aggressive and well-armed males should select males that are smaller than themselves, to avoid injuries during pair formation and mating. This hypothesis predicts assortative mating by size in such species, and in previous research, this was confirmed to occur in two skua species. This study presents, for the first time, biometric data for Falkland Skuas Stercorarius antarcticus antarcticus based on large sample sizes. Despite the clear RSD, we found no assortative mating by size, which could be related to the low divorce rates and few opportunities for mate selection in this population. Our results highlight the need for further work to find an explanatory hypothesis for the evolution and maintenance of reversed size dimorphism in skuas.
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Acknowledgements
To all who helped with fieldwork along the years, particularly Ian Strange, Georgina Strange, Miguel Lecoq, José Pedro Granadeiro, Letizia Campioni, Francesco Ventura and Amanda Kuepfer. The New Island Conservation Trust, and more recently Falklands Conservation supported field studies on New Island through the supply of research facilities. We also acknowledge helpful comments and suggestions provided by the referee Jeroen C. S. Creuwels and one anonymous referee.
Funding
This work was funded by the Fundação para a Ciência e a Tecnologia (FCT, Portugal) through the projects: UIDB/04292/2020 and UIDP/04292/2020, granted to MARE. The Falkland Islands Government provided formal permits and funding through the Environmental Studies Budget.
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PC designed and coordinated the research and carried out fieldwork. CP analysed the data. CP and PC jointly wrote the paper.
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Pich, C., Catry, P. Body size, assortative mating and divorce rates in a little-known skua taxon, the Falkland Skua Stercorarius antarcticus antarcticus. Polar Biol 45, 959–963 (2022). https://doi.org/10.1007/s00300-022-03035-2
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DOI: https://doi.org/10.1007/s00300-022-03035-2