Demography, traits and vulnerability to urbanization: can we make generalizations?

摘要

Human-induced land cover change threatens species diversity and ecosystem services. The rapid pace of current change makes predicting species' declines imperative, but leaves little time for thorough study of all species. One solution is to make generalizations about species' vulnerability to urbanization based on traits common among studied species in decline. To date, most generalizations about traits associated with species' declines in response to urbanization are based on presence or abundance, or detailed studies of a few species. If these generalizations broadly reflect responses to urbanization, they should hold across the mechanisms driving patterns of abundance, such as survival or reproduction. Across 68 bird species in the north-eastern USA, we investigated how food preference, nest location, habitat preference, migration distance, number of broods, clutch size, body mass and an interaction between urbanization and these traits affected survival and reproduction. Mass was the strongest predictor of survival, followed by number of broods, migration distance and nest location. Nest location was the strongest predictor of reproduction, followed by migration distance. No interaction between urbanization and species' traits affected survival; however, differences in response to urbanization among species with different food preferences, migration distances, masses, nest locations and number of broods were important in predicting reproduction.Synthesis and applications. We found that some traits influenced demographic rates even though they were not associated with urbanization; identifying differences in species' baseline demographic rates, irrespective of urbanization, is needed to guide management objectives. Reproduction, but not survival, was influenced by urbanization, suggesting that management in our region of study should target increasing suitable nest sites and reducing nest predation. Determining traits associated with demographic rates and urbanization across broad geographic extents can provide new insights for species' management and help guide conservation initiatives.