Meeting Abstract

P3.4  Saturday, Jan. 5  Reproductive Timing in Geographically Distinct Subspecies of Junco BERGEON, C.M.*; CAIN, K.E.; KETTERSON, E.D.; Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington cbergeon@indiana.edu

Most north-temperate birds use photoperiod as a predictive cue for the appropriate timing of seasonal breeding. Other environmental cues (e.g., food, moisture, temperature) can also interact with photoperiod to �fine-tune� reproductive responses of birds to a specific local environment. Appropriate regulation of the hypothalamo-pituitary-gonadal (HPG) axis ensures that timing of reproduction occurs under optimal local conditions, which is fundamental for reproductive success. To assess the relative importance of day length and other environmental cues in determining reproductive responsiveness, we compared seasonal duration of readiness to breed in two populations of Dark-eyed juncos (Junco hyemalis) by measuring the sensitivity of the HPG axis to stimulation by exogenous Gonadotropin Releasing Hormone (GnRH). Response to GnRH challenges is known to decline seasonally in the Carolina junco (J. hyemalis carolinensis), a subspecies of the Dark-eyed junco that breeds in cool, moist environments in the Appalachian mountains of Virginia. Little is known, however, about the breeding ecology and timing of the white-winged junco (J. hyemalis aikeni), a subspecies endemic to the Black Hills of South Dakota, where it is far hotter and drier. During 2007, we captured, measured for morphological features, and subjected male white-winged juncos to a GnRH challenge at different time points from May-July. We compared the white-winged junco to the Carolina junco, predicting that the population occupying the hotter, drier habitat would have the shorter breeding season. Comparing responses shown by individuals from locally adapted populations to a GnRH challenge will provide insights into the environmental regulation of breeding.