Introduction

Urban areas worldwide share many features, including high human population densities, the presence of high levels of chemical input to air, water and soil, and the redirection and/or piping of above-ground water flows. As habitat for fauna, their other distinctive features include planted and maintained lawns and gardens, many simple and impervious surfaces (e.g. buildings, roads), patches of remnant native vegetation, and a liberal supply of human food scraps and wastes (McDonnell and Pickett,1990; Marzluff et al., 2001; Nilon, Chapter 10; van der Ree, Chapter 11). These features also show characteristic spatial variation. In commercial and industrial domains, built structures dominate the available space, whereas in suburban residential areas, buildings are interspersed with gardens and lawns, which in turn may vary in size and nature. There is often an ‘exurban’ sprawl (Marzluff, 2001; Miller et al., 2001) containing residential areas which have larger allotment sizes, lower densities of dwellings, and more land occupied by lawns or vegetation. These global similarities are driven by trans-national export of technologies and cultures.

We might expect such similarities in environmental structure and function to produce worldwide similarities in the nature of urban wildlife assemblages. The notion that there are types of ecosystem which occur patchily across different continents (‘biomes’ sensu Begon et al., 1990) is familiar to ecological science. Examples include rainforests, savanna woodlands, heathlands, deserts and saltmarshes. While the organisms in a particular biome may differ in taxonomy, phylogeny and diversity between continents, they show parallel or convergent adaptations.