Generalists are the most urban-tolerant of birds: an analysis of ecological and life history traits using a novel continuous measure of bird responses to urbanization

7 January 2019

Callaghan, Corey; Major, Richard; Wilshire, John; Martin, John; Kingsford, Richard; Cornwell, William

Identifying which ecological and life history traits influence a species’ tolerance to urbanization is critical to understanding the trajectory of biodiversity in an increasingly urbanizing world. There is evidence for a wide array of contrasting patterns for single trait associations with urbanization. In a continental-scale analysis, incorporating 477 species and > 5,000,000 bird observations, we developed a novel and scalable methodology that evaluated the ecological and life history traits which most influence a species’ adaptability to persist in urban environments. Specifically, we assigned species-specific scores based on continuous measures of response to urbanization, using VIIRS night-time light values (i.e., radiance) as a proxy for urbanization. We identified generalized, phylogenetically controlled patterns: bird species which are generalists (i.e., large niche breadth), with large clutch size, and large residual brain size are among the most urban-tolerant bird species. Conversely, specialized feeding strategies (i.e., insectivores and granivores) were negatively associated with urbanization. Enhancement and persistence of avian biodiversity in urban environments probably relies on protecting, maintaining, and restoring diverse habitats serving a range of life history strategies.