Cooperative Fish and Wildlife Research Units Program: Arizona
Education, Research and Technical Assistance for Managing Our Natural Resources

In this study, researchers propose to quantify the importance of riparian woodlands to bird communities in Sonoran Desert national parks. This study will occur in a number of replicate sites that are characterized by riparian woodland vegetation but vary in the amount and extent of surface water present. Specifically, they will study avian abundance, species richness, and reproductive health within these riparian woodlands while at the same time quantifying the presence and abundance of surface water, vegetation parameters, and abundance of invertebrates. Hypotheses. Researchers will test the following statistical hypotheses: Ho: riparian areas have higher avian species richness than the surrounding landscape Ho: riparian areas have higher avian abundance than the surrounding landscape (for each species) Ho: amount of standing water in the 50m surrounding a survey point is positively correlated with the species richness of breeding birds in the area Ho: amount of standing water in the 50m surrounding a survey point is positively correlated with abundance in the area (for each species) Ho: clutch size is higher in riparian areas with substantial amounts of standing water compared to riparian areas lacking standing water (for a subset of focal species) Ho: nestling growth rates are higher in riparian areas with substantial amounts of standing water compared to riparian areas lacking standing water (for a subset of focal species) Ho: probability of nest depredation is lower in riparian areas with substantial amounts of standing water compared to riparian areas lacking standing water (for a subset of focal species) Ho: annual site fidelity is higher in riparian areas with substantial amounts of standing water compared to riparian areas lacking standing water (for a subset of focal species) Ho: insect abundance is positively correlated with amount of standing water Ho: surface water explains a significant amount of variation in avian species richness Perhaps more important than the tests of these hypotheses, we will estimate the extent to which riparian areas (and standing water) increase bird abundance and species richness. Model development and the parameter estimates of effect size will allow investigators to predict how proposed groundwater withdrawal of a certain magnitude will affect the abundance and species richness of birds in Saguaro National Park and other NPS units in the southwestern U.S.