Environmental drivers of variability in population and individual foraging strategies

• Main Author: Trevail, AM
• Other Authors: Patrick, Samantha C, Green, Jonathan, Sharples, Jonathan
• Format: Thesis
• Language: English
• Published: 2019
• Subjects: rissa tridactyla
• Online Access: http://livrepository.liverpool.ac.uk/3059442/; http://livrepository.liverpool.ac.uk/3059442/1/201132122_Oct2019.pdf

Efficient foraging can offer individuals a key opportunity to maximise fitness, with important consequences for population dynamics, species distributions, and ecosystem processes. The constant quest to minimise costs and maximise resource gains has given rise to a diverse range of movement behaviours among animals, the complexities of which we are continually uncovering as we accumulate more data, advance technology and develop methods. We know that animals typically forage on patchy resources that seldom stay constant in space or time. However, it remains unknown whether the degree of resource patchiness, or resource heterogeneity, can shape the costs and benefits of foraging, thus affecting foraging movements and population dynamics of animals. The overall aims of this study were therefore to use environmental, movement, and reproductive success data to understand how resource heterogeneity can drive individual and population foraging behaviour. We focus on the ecology of black-legged kittiwakes, Rissa tridactyla, which are a model species for such questions. As central place breeders that feed solely at the surface, kittiwakes are sensitive to changes in prey availability within the environment around their colony. Furthermore, kittiwakes have been widely studied as an ecosystem indicator species, and so we can build upon prior knowledge and benefit from a large body of existing data. To determine foraging behaviour I use GPS tracking data from 15 colonies around the UK and Ireland collected during the breeding seasons between 2010 and 2017; totalling 415 individuals and 1567 foraging trips. These tracking data were combined with environmental data to determine foraging habitat selection and variability over a predictable cycle, and to characterise environmental heterogeneity, as a proxy for resource heterogeneity, within the foraging range of kittiwakes at each colony. I compare environmental heterogeneity to foraging dynamics and reproductive success to understand the potential fitness costs and benefits ...