Meeting Abstract

P2.131  Tuesday, Jan. 5  Effects of climate-related variance in environmental conditions on reproductive timing and productivity in a high altitude and high latitude passerine (Empidonax oberholseri). PEREYRA, M.E.; University of Tulsa maria-pereyra@utulsa.edu

Global warming and altered frequency and duration of El Nino/Southern Oscillations may be changing precipitation patterns along the western edge of North America. One manifestation has been a decline in winter snowpack at lower elevations, but more variable snowpacks at high elevations in the western and southwestern U.S. Long-term studies of two subalpine flycatcher populations (one at high elevation, in the Sierra Nevada, and one at high latitude in northern British Columbia) indicated greater variability in time of breeding onset in the Sierran birds. This variability was largely a function of late winter and early spring snowpack, factors strongly affected by prevailing climatic influences and ENSO conditions. Winter snowpack influenced reproductive timing directly, through effects of snow water content and temperature on spring melt schedules and plant phenology, and indirectly through an array of effects on local microclimatic conditions such as ambient temperature. Effects on time of breeding onset, clutch size and fledgling production were strong in both populations, but there was little effect on time of breeding termination, even in years of late melt. In years of light to moderate snowpack, females laid earlier, fledged more chicks per nest and were more likely to renest if nest failure occurred. In years of heavy snowpack, delayed laying resulted in smaller clutches and decreased probability of renesting. Unpredictable conditions associated with more frequent El Ninos could select for shifts in habitat preference in southwestern portions of this species’ range where conditions may become wetter, and could favor northward and interior continental range expansion, where the same climatic drivers may lead to more arid winters and earlier spring melt.