Evolutionary consequences of bird feeding

Bird feeding, that is intentional feeding through the provision of food to free-living birds, is a widespread and extremely popular practice in urban areas throughout Europe. As such, it drastically alters the type, the quantity and the spatial and temporal distribution of food available for birds within the urban space. By modifying bird foraging behaviour, bird feeding is likely to have consequences for the evolution of birds in urban environments, especially by exerting selective pressures (e.g. on beak morphology, behaviour, etc.) and/or by shaping gene flow within the urban landscape. Although bird feeding may be a key driver of the phenotypic and genetic differences observed between urban and rural bird populations, we critically lack understanding on the role that bird feeding plays on the evolution of birds in urban environments. In this project, I will address two main questions: 1) How does bird feeding shape genetic connectivity within the urban mosaic? and 2) How is bird feeding associated with patterns of allele selection and selective disappearance (i.e. differential mortality rates between individuals of different phenotypes)? In practice, I will collect phenotypic (e.g. beak size, plumage colouration), genomic (i.e. genotypes at 95 microsatellite loci and at several candidate genes) and spatiotemporal data (i.e. bird location at multiple events) in two tit species, namely the great tit (Parus major) and the blue tit (Cyanistes caeruleus), to infer gene flow and selection. Importantly, this project will use a unique grid sampling design, as well as state- of-the-art methods in landscape genetics and capture-recapture modelling: by using such an individual-based landscape approach (rather than the common population-based approach), I will assess the diversity of habitats within the urban landscape, which will allow to identify the drivers of phenotypic variation and genetic structure within the urban landscape. In doing this, I expect to demonstrate, for the first time, that (i) the genetic structure of great tit and blue tit meta-populations vary between seasons as the result of short-scale movements towards areas rich in bird feeders during winter, (ii) bird feeding shapes gene flow, either by facilitating movements within the urban mosaic or, on the contrary, by increasing sedentary behaviours, and (iii) bird feeding explains genetic and phenotypic variations, either by benefiting to some genotypes/phenotypes (e.g. longer beaks) or, on the contrary, by relaxing selection.