BIRD TRENDS IN NATIONAL PARKS OF THE SIERRA NEVADA: HAS RECENT CLIMATE MASKED A GENERAL DECLINE IN POPULATION DENSITY?
|Chris Ray; The Institute for Bird Populations; email@example.com; Robert L. Wilkerson, Rodney B. Siegel, Mandy L. Holmgren, Sylvia A. Haultain|
Avian monitoring within national parks of the Sierra Nevada Inventory and Monitoring Network began in 2011, with the goal of detecting trends to inform the conservation of birds and their habitats. We used 2011-2019 data from 2408 point-count stations to estimate trends in population density for 62 species in several parks: Devils Postpile National Monument, Sequoia and Kings Canyon National Parks and Yosemite National Park. Point-count data were analyzed in a Bayesian hierarchical modeling framework, accounting for imperfect detection and effects of covariates on bird detection and density. Results suggest relative stability of bird population density in these parks during the monitoring period, with up to 10 species declining, 38 remaining stable and 14 increasing in density. Population density varied inversely with precipitation-as-snow in at least half of our analyses. This relationship, combined with a series of dry winters in the Sierra Nevada, might have helped stabilize bird densities in these national parks during the monitoring period. However, trends varied among parks and--for most species--population density declined inversely with year, indicating a temporal decline that was not completely ameliorated by the apparently favorable climate during recent years in these parks, and fueling concern for the future.