Individual migration strategy fidelity but no habitat specialization in two congeneric seabirds

Benjamin Merkel,Svein‐Håkon Lorentsen,Sébastien Descamps,David Grémillet,Hallvard Strøm,Harald Steen,Kjell E Erikstad,Francis Daunt,Maria Gavrilo,Sarah Wanless,Geir H Systad,Þorkell Lindberg Þórarinsson,Mike P Harris,Nigel G Yoccoz,Aleksey V Ezhov,Tone K Reiertsen

doi:10.1111/jbi.13883

Abstract

AbstractAimIn migratory species, individuals often use fixed and individual‐specific migration strategies, which we term individual migration strategy fidelity (IMSF). Our goal was to test if guillemots have flexible or fixed individual migration strategies (i.e. IMSF), if this behaviour is consistent across large parts of the genus’ range and if they were philopatric to geographical sites or a habitat feature.LocationNorth Atlantic.TaxonUria spp.MethodsWe quantified consistent individual differences in inter‐annual spatial distribution and habitat occupied throughout the non‐breeding period using a large geolocator tracking dataset of 729 adult seabirds breeding at 13 colonies across the Northeast Atlantic and repeatedly tracked up to 7 years over a 9‐year period. Additionally, we used a similarity index to calculate relative fidelity to either geographical sites or habitats and linear mixed‐effects models to assess persistence of spatial site fidelity over multiple years.ResultsBoth guillemot species exhibited IMSF across a large part of the genus’ range which persisted over multiple years. Individuals of both species and almost all colonies showed fidelity to geographical sites and not to specific habitats.Main conclusionsGuillemots show IMSF that is best explained by site familiarity (fidelity to specific sites) rather than habitat specialization (fidelity to specific habitats). In the context of rapidly changing environments, favourable habitats may permanently shift locations and hence species displaying IMSF driven by site familiarity—such as the genus Uria—may not be able to adjust their migration strategies sufficiently fast to sustain individual fitness and ensure population persistence.

Highlights

Migratory animals face many challenges in a rapidly changing world (Robinson et al, 2009; Wilcove & Wikelski, 2008) as individuals need to structure their annual schedule to maximize availability of spatially and seasonally fluctuating resources (Alerstam, Hedenström, & Åkesson, 2003; Bridge, Ross, Contina, & Kelly, 2015)
Main conclusions: Guillemots show individual migration strategy fidelity (IMSF) that is best explained by site familiarity rather than habitat specialization
Less evidence exist for site fidelity outside the breeding season here termed ‘Individual migration strategy fidelity’ (IMSF) when within-individual variation in the use of space during the non-breeding period is less than that across the population as a whole

Summary

Introduction

Migratory animals face many challenges in a rapidly changing world (Robinson et al, 2009; Wilcove & Wikelski, 2008) as individuals need to structure their annual schedule to maximize availability of spatially and seasonally fluctuating resources (Alerstam, Hedenström, & Åkesson, 2003; Bridge, Ross, Contina, & Kelly, 2015). Many migrants, such as seabirds, are long-lived species (Schreiber & Burger, 2001). IMSF could be the cause or a consequence of other types of specialization, such as in diet or habitat with contrasting implications in the context of climate change

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Results

Discussion

Conclusion