Becoming citizens: Avian adaptations to urban life

Abstract

Although cities have existed for some millennia, it has been only in the last few centuries that they have expanded to become a dominant feature of the landscape. Their growth displaces original habitats and creates new ones, facing birds with the challenge of adjusting their behaviour, physiology and life histories to the novel conditions or be displaced into a shrinking and also increasingly altered rural landscape. Here we identify the salient features-habitat structure, seasonality, interspecific interactions and pollution-in which cities differ from natural environments and to which birds must adjust. Then we describe the several ways in which urban birds have been found to differ from their rural counterparts. Finally, we evaluate whether these differences constitute adaptations to urban conditions or whether they are expressions of pre-existing adaptations to natural conditions, such as behavioural plasticity, which also permit the colonisation of urban habitats.