Meeting Abstract

109.1  Sunday, Jan. 6  Influence of temperature on non-breeding HPG-axis activity in northern cardinals. JAWOR, J.M.*; HOOKER, J.D.; University of Southern Mississippi; University of Southern Mississippi jodie.jawor@usm.edu

In seasonally breeding birds, change in day length is a very common cue used to track seasonal change and initiate breeding, however, not all species use changing day length as their primary environmental cue. Many species rely on resources that are irregularly spaced in time and location for reproduction and these non-photic cues can be more influential than changes in day length. Northern Cardinals (Cardinalis cardinalis) show year-round levels of testosterone as well as broad timing in when they initiate reproduction and the behaviors associated with reproduction, suggesting that they may not use changes in day length as the sole control for transitions between non-breeding and breeding states. Here we used exogenous gonadotropin-releasing hormone (GnRH) challenges to investigate hypothalamic-pituitary-gonadal (HPG) axis activity and compare HPG axis activity with daily temperature prior to the winter solstice, when day lengths begin to increase. We found that male response to GnRH did not co-vary with temperatures in a predictable pattern. In females response was more complex and tended to co-vary with temperature. We suggest that in male cardinals, once they have an active HPG axis, no further modification of activity may be beneficial, while females may benefit by having a physiological response system that can more closely track environmental change.