PEREYRA, Maria Elena*; MORTON, Martin L.; University of Tulsa; University of Tulsa: Weather and predation as selective factors driving nest-site selection in two populations of dusky flycatcher

We compared nest-site selection in two widely separated populations of dusky flycatcher (Empidonax oberholseri), one located in the eastern Sierra Nevada of California, at Tioga Pass (37�N), and one near Atlin, British Columbia (59�N). Both populations utilize subalpine habitats of similar vertical structure and plant composition (subalpine willow, aspen and lodgepole pine) with seasonal changes in nest-site selection that reflect concomitant changes in environmental conditions such as snow depth and local canopy characteristics. In both populations, aspects of nest-site selection such as nest height, nest-site substrate and surrounding vegetation are largely reflective of plant species abundance and vegetative phenology, with one notable exception. Lodgepole pine forests, which are abundant components of dusky flycatcher breeding habitat in both the Sierra Nevada and in northern British Columbia, are frequently used for nesting in the Sierran population but never in the Atlin population. We evaluate the importance of predation and weather as selective factors influencing behavioral characteristics such as nest-site selection at the population level and speculate on the importance of these mortality factors in shaping phenotypic plasticity in substrate preferences.