Black-billed Magpies (Pica pica) adjust nest characteristics to adapt to urbanization in Hangzhou, China

Although many bird species worldwide are colonizing urban environments, the ecological processes underlying the responses to urbanization remain unclear. Here we examined the responses of Black-billed Magpies ( Pica pica (L., 1758)) to urbanization across an urban–rural gradient by assessing nest locations, nest height, and available nest sites at six habitats (mountains, farmlands, riparians, urban parks, strips of street trees, building areas) in Hangzhou, China. In each habitat, we categorized used and available nest sites as urban (e.g., chimneys, antenna or cable poles, ledges, and open roofs on buildings) or natural (e.g., trees) nest sites. We found 147 magpie nests in five of the six habitats, and no nests in mountains. The use of urban nest sites by magpies differed significantly across habitats, and it increased significantly with the availability of urban nest sites along the urban gradients. Nest height of magpies differed significantly across habitats, and it increased significantly with urbanization intensity. The increase in nest height in urban environments can be attributed to the increases in human disturbance (the number of pedestrians). Our results indicate that magpies can adjust their nest characteristics in response to urbanization, and that nesting behavior shifts may aid them to adapt to urban systems.