"This proposal takes the disciplines of cognitive and evolutionary biology into a natural setting on an unprecedented scale to explore a variety of causes and consequences of individual variation in cognitive ability.The study system is a series of great tit (bird) sub-populations across habitat fragments of very different quality, consisting of conifer plantation and natural broad-leaf woodland. Great tits are year-round residents that use a wide range of patchily distributed food types, suggesting an important role for different cognitive processes. They are readily tagged and use nest boxes freely, making them easy to monitor remotely.In the first work package, the aim is to examine social and individual causes of variation in different indicators of cognitive ability (e.g. associative learning ability), to determine whether these differences are linked to life history variation, and if so, to ask if this necessarily leads to selection for higher cognitive performance, or instead whether cognitive ability also comes with costs.Natural selection rarely acts on traits in isolation and is dependent on current conditions. Thus the work package will also explore whether observed patterns are moderated by other functionally relevant phenotypic variation (personality and bill morphology) or are dependent on habitat quality. Ultimately the aim will be to combine estimates of heritability generated from pedigree animal models with selection to measure the predicted micro-evolutionary responses.In the second work package, the aim is to explore the functional mechanisms underlying links between cognitive ability and life history variation, testing whether cognitive variation is linked to: i) space use in the natural environment, ii) foraging decisions and diet profiles, and iii) parental care trade-offs.In summary the proposal will be an unprecedented examination of the evolutionary and ecological processes that drive variation in cognitive ability."