A UCLA-led research team created an ‘urban association index’ that describes how closely bird species are associated with living in urban settings. With more of the planet being consumed by urbanization, the scientists write that a dramatic loss of biodiversity is likely unless there are practical plans to preserve it. Urban bird species tend to be smaller and less territorial and have greater ability to fly long distances than other species; they also tend to have broader dietary and habitat niches and to live at a wider range of elevations.