Meeting Abstract

25.2  Friday, Jan. 4  Testosterone and neuroplasticity in a tropical bird SMALL, TW*; BRENOWITZ, EA; MOORE, IT; Virginia Tech; University of Washington; Virginia Tech twsmall@vt.edu

Seasonally breeding birds in temperate/arctic latitudes typically use changes in day length to time reproduction. Associated with seasonal reproduction and behavior are seasonal changes in brain structure and function. This neuroplasticity includes seasonal growth of the neural song control system that is mediated by testosterone. The role of testosterone in neuroplasticity and singing behavior has been well documented in many northern latitude species. However, the majority of bird species are tropical and thus experience changes in day length that are small and less likely to be associated with seasonality. We have previously documented that an equatorial bird, the rufous-collared sparrow (Zonotrichia capensis) can exhibit seasonal neuroplasticity much like their northern temperate congener the white-crowned sparrow (Z. leucophrys) despite not experiencing significant changes in day length. In the current study, we investigated if testosterone mediates neuroplasticity of the song control system and singing behavior in this equatorial species in a similar manner to their temperate congeners. We treated birds with testosterone or blank implants and measured the size of the neural song control nuclei HVC, X, and RA, as well as reproductive morphology and singing behavior. Preliminary results suggest that testosterone treatment stimulated the reproductive system while controls maintained fully regressed reproductive systems indicating that this equatorial species exhibits some responses to testosterone that are similar to their northern congeners. However testosterone treatment had no effect on singing behavior.