Population Viability of Golden‐cheeked Warblers in an Urbanizing Landscape

摘要

Population viability analyses can assess species persistence under current or simulated future conditions and guide conservation and management efforts for species of concern. We evaluated population viability of an endangered songbird, the golden‐cheeked warbler (Setophaga chrysoparia), over a 50‐year period using empirically derived population parameters collected from 2009 to 2015 on the Balcones Canyonlands Preserve (BCP), Travis County, Texas, USA. Assuming the extent and quality of habitat within the BCP does not change, the population remained stable with a population size of approximately 1,800 males, adult survival of 0.57, seasonal productivity of 1.32 male fledglings/territory, and assumed juvenile survival of 0.40. Population viability, however, was sensitive to changes in vital rates. The population declined toward local extinction when vital rates were at the low end of rates considered (0.47 adult survival, 1.14 male fledglings/territory, 0.28 juvenile survival), but had little tono probability of local extinction when vital rates were at the upper end (0.67 adult survival, 1.50 male fledglings/territory, 0.44 juvenile survival). Obtaining accurate estimates of juvenile survival remains problematic, but if juvenile survival is aslow as previously reported elsewhere (0.28), the stability observed during the years of our study could be due to immigration of individuals displaced by habitat loss in the surrounding landscape. Increased carrying capacity, which served as a proxy forincreased habitat quality within the BCP, was insufficient to sustain the population when productivity was low, illustrating the need for adequate seasonal productivity. Consistent with previous studies, our findings underscore the importance of managing for high‐quality breeding habitat and maintaining connectivity with other large habitat patches to promote the long‐term viability of the species. We suggest monitoring survival and productivity of high‐concern species may be justified because assessment of status from abundance alone can be confounded by immigration and other factors.