Roy, J.; Dominoni, D. M.

Due to urbanisation the nest material availability changes and birds are shown to change their nesting behaviour. The study on passerines about the change in nest material use and its implications is scarce. We studied the changes in the nest composition of blue tits as a comparison between urban and rural habitats and assessed its implications on their breeding success. There was a significant decrease in the number of natural materials and an increase in anthropogenic materials in urban nests. The amount of moss acts as a strong predictor of fledgling success. Earlier urban nests showed a higher amount of anthropogenic material, which could be an indication of parent quality. In the rural habitats, the presence of anthropogenic materials along with feathers might show preferential selection as an extended sexual phenotype, while in urban habitats, the anthropogenic materials is often present as the structural component of the cup. Quantifying the availability of natural materials is needed to allow a clearer interpretation of the preferential selection of anthropogenic materials in urban habitats.