INFLUENCES OF RIVER REGULATION AND DROUGHT ON BREEDING BIRDS BELOW O'SHAUGNESSY DAM
Sarah L Stock; Yosemite National Park; P.O. Box 700, El Portal, CA, 95318; (209) 379-1435; sarah_stock@nps.gov; Michelle A. Desrosiers, Lynn N. Schofield, Breeanne K. Jackson
Dams and other water control structures have altered every large river in the United States, making them the most pervasive human impacts to riparian systems in the country. Understanding the complex and varied ecological implications of river regulation is critical, because streamside riparian habitats support a disproportionate high level of species diversity. We used birds as indicators of riparian ecosystem integrity and assessed how bird abundance and species richness changed in relation to different streamflow characteristics between 2007 and 2017 in Poopenaut Valley immediately downstream of O’Shaughnessy Dam, Yosemite National Park. We found that prolonged low flows and overall water availability affected abundance and species richness of breeding birds in Poopenaut Valley. As the number of low-flow days increased, avian abundance and species richness decreased; and as higher annual daily water releases increased, the abundance of riparian focal species increased. These findings have implications for increasingly variable hydrological conditions that are predicted under climate change scenarios. This study indicates that water managers can manipulate the flow regime to match flows to historic condition and offset expected increased annual variability due to climate change, to benefit birds and the ecosystem.
Yosemite Restoration II