Worldwide urbanization and its effects on birds

* Final gross prices may vary according to local VAT.

Get Access

Abstract

Human populations are increasing and becoming predominantly urban. Resulting land cover changes reduce, perforate, isolate, and degrade bird habitat on local and global scales. I review: 1) urbanization of the Earth, and 2) published studies of bird responses to human settlement, and then: 3) suggest how and why birds respond to settlement. In a slight majority of studies, bird density increased, but richness and evenness decreased in response to urbanization. The most consistent effects of increasing settlement were increases in non-native species of birds, increases in birds able to nest on buildings (esp. swifts and swallows), increases in nest predation, and decreases in interior- and ground-nesting species. Effects of urbanization on hawks, owls, and cavity nesters were less consistent, in part being dependent on the surrounding habitat. The factors favoring species in urbanizing areas appear simpler than those reducing species. Increased availability of food was primary among factors benefiting species; predator reduction, reduced human persecution, and habitat enhancement were less important. Decreased habitat availability, reduced patch size, increased edge, increased non-native vegetation, decreased vegetative complexity, and increased nest predation were commonly associated with bird declines in response to human settlement. Urban planners and policy makers can profoundly affect how and where cities grow. Avian ecologists can help inform these important decisions by: 1) quantifying how the pattern of settlement affects birds and 2) understanding how bird populations and resulting communities change along entire gradients of urbanization.