Urbanization,avian communities,and landscape ecology

Abstract

Human settlement is a prevalent source of land-use change worldwide. but our understanding of the effects of settlement on avian communities is limited. Settlement has been characterized as a gradient that extends from urban development to exurban and rural areas. An important advantage of the gradient approach is the potential to identify thresholds in the response of birds to settlement. Although gradients have been used in studying the effects of urbanization on birds, relatively little attention has been paid to the exurban end of the spectrum, despite the potential for this type of development to affect large expanses of habitat. Studies at relatively fine scales are useful for investigating the influence of proximate factors. such as vegetation structure and composition. on birds in human-dominated areas. However, such studies must be coupled with investigations at broader scales to gain a more complete understanding of the ways that human settlement affects bird communities. Urban-wildland gradients can be quantified using remotely-sensed imagery in combination with data on the intensity and pattern of settlement. However, metrics used to describe patterns of settlement are only useful to the extent that they represent something meaningful to birds. The extent of the landscape mosaic surrounding a study site that needs to be quantified depends on the goals for a particular study. We propose a research protocol for studying the effects of settlement on birds that may be useful at multiple scales. Study sites are distributed among land-cover and settlement types, and replicated surveys are progressively aggregated from small to large scales. These data serve as the basis for interpolation, using traditional statistical tools and geostatistical methods, to areas not sampled. To be effective, conservation must be focused on landscape mosaics, not habitat patches. Areas where people live and work are important components of these mosaics.