Environmental heterogeneity promotes individual specialisation in habitat selection in a widely distributed seabird

Alice M Trevail,Gail Robertson,Mark Bolton,Peter I Miller,Jonathan Sharples,Samantha C Patrick,Jonathan A Green,Jeff A Polton,Ellie Owen,Francis Daunt,Stephen Newton,Stephanie M Harris

doi:10.1111/1365-2656.13588

Abstract

Individual specialisations in behaviour are predicted to arise where divergence benefits fitness. Such specialisations are more likely in heterogeneous environments where there is both greater ecological opportunity and competition-driven frequency dependent selection. Such an effect could explain observed differences in rates of individual specialisation in habitat selection, as it offers individuals an opportunity to select for habitat types that maximise resource gain while minimising competition; however, this mechanism has not been tested before. Here, we use habitat selection functions to quantify individual specialisations while foraging by black-legged kittiwakes Rissa tridactyla, a marine top predator, at 15 colonies around the United Kingdom and Ireland, along a gradient of environmental heterogeneity. We find support for the hypothesis that individual specialisations in habitat selection while foraging are more prevalent in heterogeneous environments. This trend was significant across multiple dynamic habitat variables that change over short time-scales and did not arise through site fidelity, which highlights the importance of environmental processes in facilitating behavioural adaptation by predators. Individual differences may drive evolutionary processes, and therefore these results suggest that there is broad scope for the degree of environmental heterogeneity to determine current and future population, species and community dynamics.

Highlights

Through habitat selection, individuals optimise their use of the environment to maximise fitness (Rosenzweig, 1981)
This trend was significant across multiple dynamic habitat variables that change over short time-scales and did not arise through site fidelity, which highlights the importance of environmental processes in facilitating behavioural adaptation by predators
As predicted by our conceptual framework, we demonstrate that kittiwakes showed greater individual specialisation in habitat selection in more heterogeneous environments

Summary

| INTRODUCTION

Individuals optimise their use of the environment to maximise fitness (Rosenzweig, 1981). Heterogeneity in the physical environment can create opportunities to specialise on different habitat types (Araújo et al, 2011; Bolnick & Ballare, 2020), potentially at the cost of greater intraspecific competition if many individuals select patches with similar habitat characteristics (López-Bao et al, 2011; Trevail, Green, Sharples, Polton, Miller, et al, 2019). Because environmental heterogeneity in the dynamic marine environment reflects the complexity of habitat types that shape resource fluctuations over both space and time (Trevail, Green, Sharples, Polton, Arnould, et al, 2019), we establish whether habitat selection (i.e. tracking habitat types), rather than fidelity to particular foraging site locations, is the mechanism by which individual specialisations in habitat selection while foraging arise in these populations (Merkel et al, 2020). We test whether environmental heterogeneity influences a population's degree of individual fidelity to specific foraging sites

| MATERIALS AND METHODS

| DISCUSSION

Findings

| CONCLUSIONS