To graze or gorge: consistency and flexibility of individual foraging tactics in tits.

An individual's foraging behaviour and time allocated to feeding have direct consequences for its fitness. Despite much research on population-level foraging decisions, few studies have investigated individual differences in fine-scale daily foraging patterns among wild animals. Here, we explore the consistency and plasticity of feeding tactics of individual great tits (Parus major) and blue tits (Cyanistes caeruleus), using a grid of 65 automated feeding stations in a 385-ha woodland, during three winters. We use a principal component analysis to describe individual variation in six feeding parameters and examine how these differences covary with dominance-linked attributes (species, age and sex), the personality trait 'exploration behaviour', distance to territory and local competition intensity. Analysis of 933 086 feeder visits by 3134 individuals revealed that the majority of variation in the timing of feeding was explained by two principal components. PC1 ('binge-eating'), accounting for 38% of variation, captured temporal clustering of feeding, with high repeatability both within and between years (r range: 0·42-0·55). PC2 ('transience'), accounting for 27% of variance, described how much individuals used feeders and was also repeatable (r: 0·34-0·62). While exhibiting consistent individual differences, birds also showed flexibility in foraging patterns, binge-eating less and using feeders more when they experienced greater local competition. Individuals in behaviourally dominant states (great tits, males and adults) binged more than subordinate birds (blue tits, females and juveniles) when their territories were distant from feeding stations. Moreover, great tits and males used feeders more than blue tits and females respectively, while birds feeding further from their territory used feeders less than those feeding closer. 'Exploration behaviour' was unrelated to both measures of daily foraging behaviour. This study presents some of the first evidence that birds use consistent alternative foraging tactics at a fine temporal scale. Individuals are consistent in their tactics, and also adjust their foraging behaviour with changes in local competition. Hence, studies of foraging behaviour should consider the extent to which such individual-level variability in foraging behaviour is under selection.

The role of social and ecological processes in structuring animal populations: a case study from automated tracking of wild birds.

Both social and ecological factors influence population process and structure, with resultant consequences for phenotypic selection on individuals. Understanding the scale and relative contribution of these two factors is thus a central aim in evolutionary ecology. In this study, we develop a framework using null models to identify the social and spatial patterns that contribute to phenotypic structure in a wild population of songbirds. We used automated technologies to track 1053 individuals that formed 73 737 groups from which we inferred a social network. Our framework identified that both social and spatial drivers contributed to assortment in the network. In particular, groups had a more even sex ratio than expected and exhibited a consistent age structure that suggested local association preferences, such as preferential attachment or avoidance. By contrast, recent immigrants were spatially partitioned from locally born individuals, suggesting differential dispersal strategies by phenotype. Our results highlight how different scales of social decision-making, ranging from post-natal dispersal settlement to fission-fusion dynamics, can interact to drive phenotypic structure in animal populations.