Urbanized birds have superior establishment success in novel environments

Many animals have adapted to the proximity of humans and thereby gained an advantage in a world increasingly affected by human activity. Numerous organisms have invaded novel areas and thereby increased their range. Here, we hypothesize that an ability to thrive in urban habitats is a key innovation that facilitates successful establishment and invasion. We test this hypothesis by relating the probability of establishment by birds on oceanic islands to the difference in breeding population density between urban and nearby rural habitats as a measure of urbanization in the ancestral range. This measure was the single-most important predictor of establishment success and the only statistically significant one, with additional effects of sexual dichromatism, number of releases and release effort, showing that the ability to cope with human proximity is a central component of successful establishment. Because most invasions occur as a consequence of human-assisted establishment, the ability to cope with human proximity will often be of central importance for successful establishment.