Meeting Abstract

P3.2  Saturday, Jan. 5  Effects of phenotypic characteristics on reproductive timing in high altitude flycatchers PEREYRA, M.E.*; University of Tulsa maria-pereyra@utulsa.edu

For migrant birds breeding at high latitudes and high altitudes, individual variation in reproductive timing can be viewed as a trade-off between the costs and benefits of breeding at the earliest possible date or delaying until some threshold of reproductive readiness is achieved. In high altitude species, factors that can influence reproductive readiness include environmental conditions such as snow pack, habitat development, temperature and weather as well as physical characteristics such as age, body size and body condition (mass and fat). In dusky flycatchers (Empidonax oberholseri) breeding at high altitude in the Sierra Nevada, females that began breeding at the earliest seasonal extremes laid larger clutches and had greater chances of fledging young. Despite this, substantial numbers of individuals delayed each year. The costs and benefits of early reproductive onset versus delay are discussed in the context of female age, size and body condition, three parameters that can influence reproduction, either directly through effects on time and energy invested in reproductive activities and clutch formation, or more indirectly, by influencing physiological responses to environmental factors.