Avian Density and Nest Survival on the San Pedro River: Importance of Vegetation Type and Hydrologic Regime

摘要: Lowland riparian vegetation in the southwestern United States is critically important for maintaining a high richness and density of breeding birds. Further investigation needed within corridors, however, to evaluate relative importance type hydrologic regime avian nest survival as targets regional conservation or restoration efforts. We estimated densities 40 bird species grouped on basis height dependence surface water gallery cottonwood-willow (Populus spp.-Salix spp.) forests, saltcedar (Tamarix shrub lands, terrace types along gradient San Pedro River, Arizona, USA. also assessed shrub-nesting insectivores herbivores. Canopy-nesting birds group 14 individual reached their greatest cottonwood forests regardless regime. Water- dependent highest both intermittent- perennial-flow stands, but certain occurred almost exclusively sites. Two brown-headed cowbird (Molothrus ater) were most abundant was stands with intermittent flows. Mesquite (Prosopis big sacaton (Sporobolus wrightii) grassland each maintained L Shrub-nesting had cottonwood, including Arizona Bell's vireo (Vireo bellii arizonae), lower proportions nests parasitized preyed upon, although 95% confidence intervals among overlapped. Nest herbivores lowest intermittent-flow saltcedar, although, again, than nonparasitized mesquite across Abert's towhee (Pipilo aberti). Riparian management that maintains heterogeneous types, floodplain comprising some stretches perennial flow, are diversity abundance River probably region. Cottonwood appear maintain