Meeting Abstract

P3.32  Monday, Jan. 6 15:30  Effects of temperature on the transition from reproduction to molt in house finches WATTS, H. E.*; VILGALYS, T. P.; Loyola Marymount University ; Loyola Marymount University hwatts1@lmu.edu

The transition from reproduction to molt is a key life history transition in the lives of birds. In this study we investigated the role of temperature as an environmental factor influencing the timing of this transition. Understanding the effects of temperature on the timing of life history events is of particular importance because ambient temperatures experienced by wild animal populations are changing as a result of global climate change. In this experiment, wild caught male house finches (Haemorhous mexicanus) were captured in April and housed from May onwards under two different temperature regimes, simulating cooler (mean max = 23.5 °C) and warmer (mean max = 30.6 °C) summer temperatures. Birds were then monitored as they transitioned from reproduction to molt. By the end of July, most birds (85%) had initiated molt, though not all birds had regressed the gonads. We found that males in the warmer treatment initiated molt earlier than did males in the cooler treatment. Circulating testosterone levels declined over the course of the experiment, but we found no difference in testosterone between the treatment groups. There was also a trend for males in the warmer treatment to delay gonadal regression compared with males in the cooler treatment. Our results suggest that warmer summer temperatures can advance the breeding-molt transition in male house finches.