Individual variation in a polar seabird: Integrating behaviour, physiology and life-history in the responses to global environmental change

McKendrick, Frederick (2025) Individual variation in a polar seabird: Integrating behaviour, physiology and life-history in the responses to global environmental change PhD thesis, University of Liverpool.

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Abstract

Within-individual variation is increasingly emerging as an important component of phenotypes due to the role it plays in shaping how organisms respond to environmental change. For instance, within-individual variability in movement may facilitate resource acquisition in stochastic environments but we have little information on how individuals differ in variability through time nor the fitness benefits at the individual level. Physiological biomarkers may quantify such benefits as they are highly responsive to resource acquisition, provide insights into periods we can’t physically observe organisms and can correlate with both reproductive success and survival. Intrinsic characteristics, such as animal personality, may shape both intrinsic variability and its consequences for fitness and therefore determine when individuals are most sensitive to changes in their environment. Throughout this thesis I explore how variation in both movement and physiology may be linked to environmental change. I investigate how personality may shape differences in phenotypic variability and what impacts this may have on fitness. I investigate these relationships across the whole annual cycle to gain a holistic understanding of when individuals are most sensitive to environmental variation. I use black-legged kittiwakes (Rissa tridactyla) breeding in the high Arctic as a model system. The Arctic is seeing rates of warming at three times the global average and so kittiwakes occupying these regions are having to adapt much faster than their temperate conspecifics. I firstly show that boldness, an important axis of personality, is related to differences in feather corticosterone, a measure of nutritional state, but that this relationship differs across the annual cycle with bolder birds being in better nutritional state than shyer conspecifics during periods of spatial constraint. However, I show the impact of environmental change on nutritional state is ubiquitous across personality types and that nutritional state is a key indicator of fitness, with feather corticosterone being negatively correlated to both reproductive success and return rates to the colony, a proxy of survival. I then show that differences in movement between personality types may explain the variation we see in nutritional state, with shyer individuals exhibiting greater variability in foraging behaviour than bolder birds, leading to lower feather corticosterone during non-breeding periods. I illustrate that within-individual variability in movement appears to be consistent across the annual cycle and may have contrasting effects on resource acquisition between breeding and non-breeding periods. I finally investigate individual variation in plasticity of foraging behaviour at fine scales, showing that individuals are highly responsive to changes in key resource patches but that this plasticity is highly context dependent on current resource availability. Interestingly, plasticity did not influence reproductive outcomes suggesting that there may be no current benefit of variability in movement within productive environments. The results of this thesis provide novel insights into why differences in resource acquisition across the annual cycle may demonstrate how individual variation is maintained within populations. I provide new evidence supporting within-individual variation as an important component of movement phenotypes and how variability may be conserved across distinct life-stages. By bringing together examples from across the phenotype, I highlight how individual variation is likely to be an important component of a populations ability to deal with both environmental stochasticity and the variable ecological constraints across the annual cycle.

Item Type:	Thesis (PhD)
Divisions:	Faculty of Science & Engineering Faculty of Science & Engineering > School of Environmental Sciences
Depositing User:	Symplectic Admin
Date Deposited:	18 Sep 2025 14:58
Last Modified:	18 Sep 2025 14:58
DOI:	10.17638/03194328
Supervisors:	Patrick, Samantha Arnold, Kathryn Jenouvrier, Stephanie Descamps, Sebastien
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3194328
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