Habitat selection by riparian songbirds breeding in southern Arizona

Identifying habitat characteristics that influence selection of nest sites can provide information necessary for understanding and managing songbird populations. We quantified patterns of nest-site selection of 7 species in a riparian songbird community (n = 162 nests) at 2 spatial scales in southeastern Arizona, USA: Bell's vireo (Vireo bellii), verdin (Auriparus flaviceps), phainopepla (Phainopepla nitens), summer tanager (Piranga rubra), northern cardinal (Cardinalis cardinalis), blue grosbeak (Guiraca caerulea), and hooded oriole (Icterus cucullatus). We compared vegetation characteristics at nests to points chosen at random both near each nest (nest-patch scale) and within the entire study area (canyon scale). At the nest-patch scale, riparian vegetation - particularly Arizona sycamore (Platanus wrightii) and netleaf hackberry (Celtis reticulata) - was selected strongly by most species. At the canyon scale, most species nested in areas with higher vegetation density and volume than available at random. Managing riparian areas to foster high vegetation density and key structural components, such as sycamore and hackberry trees, is essential for meeting the habitat requirements necessary to maintain abundant and diverse songbird communities in the arid southwestern United States and adjacent Mexico.