Roof nesting by gulls for better or worse?

Since the early 1970s in Italy, the yellow-legged gull Larus michahellis has been colonizing new kinds of nesting areas, in particular moorland and the rooftops of inhabited buildings. The incidence of rooftop colonies is now such that the yellow-legged gull has come in many urban areas to be regarded as a pest. Yet its colony structure and breeding biology in the urban situation in Italy have remained largely undocumented. This paper reports observations of yellow-legged gulls breeding in the town of Venice and in the surrounding lagoon during the 2003-2005 breeding seasons. The aim of this study was to examine the performance of birds breeding in natural and urban areas and to investigate the links between the natural and the newly established urban colony. For this, we analysed and compared factors indicative of breeder quality. Breeding performance was not substantially different in the two colonies. This suggests that gulls are successfully exploiting a new habitat, adapting to new resources, as other opportunistic species do.