Urban landscape design and bird community structure in Phoenix, Arizona: Management implications

Urbanization, with its transformations of natural biotic systems into human-dominated landscapes, has become recognized as one of the greatest threats to bird diversity throughout the world. However, certain landscape designs may mimic natural landscapes, providing mini refugia within urban areas and enabling the persistence of a natural bird community. Residential landscape design in Phoenix, Arizona is dominated by mesic (turf, water-loving), and xeric (gravel, desert-like) yards. If fine scaled vegetation structure within the residential yards differs between mesic and xeric, bird community structure should also differ between these two forms of landscape design. We tested this hypothesis by classifying transects as either mesic or xeric. We then quantified vegetation structure and perching opportunities in residential landscapes along three 100m X 40m transects around 57 of the bird monitoring locations at the Central Arizona-Phoenix Long-Term Ecological Research project. Preliminary results suggest mesic transects are dominated by tall trees (>20m) and by non-native tree species. By contrast, xeric transects are dominated by smaller, mostly native or drought-tolerant tree species. Bird communities significantly varied with fine scaled vegetation structure measures but not categorically between mesic and xeric designs. For example, the widely distributed Great-tailed Grackle is more abundant in neighborhoods with clusters of conifers and citrus trees, both non native. Future studies aim to address the mechanisms and behavioral cues responsible for the distinct bird assemblages within the different human-dominated landscapes. If particular landscape designs and vegetation structures support more native-like bird communities, then development plans could incorporate these designs in future projects.