Meeting Abstract
P1.138 Saturday, Jan. 4 15:30 Testosterone Production Capability in a Songbird during Spring Migration COVINO, K.M.*; MOORE, F.R.; MORRIS, S.R.; JAWOR, J.M.; University of Southern Mississippi; University of Southern Mississippi; Canisius College; University of Southern Mississippi covinok@gmail.com
The connection and interaction among phases of the annual cycle in migratory species are poorly understood. Testosterone may be an important signal for the onset of vernal migration in songbirds: Elevated testosterone induces migratory activity, testosterone levels increase throughout spring migration in some species and early arriving males on breeding grounds generally have higher circulating levels. Presumably, migrants must have sufficient levels of testosterone in circulation soon after arrival on the breeding grounds to facilitate necessary breeding behaviors. We investigate whether testosterone production may be modulated during migration to take advantage of beneficial effects while avoiding negative consequences of elevated testosterone en route. To do so, we determined both circulating testosterone levels as well as testosterone production capability in a boreal breeding migrant. We performed GnRH challenges via an intra-muscular injection on male and female Swainson’s Thrushes (Catharus ustulatus) at two stopover sites representing different distances remaining to the breeding grounds. Males at both locations were capable of producing more testosterone than naturally circulating levels, and capability was higher in males sampled closer to their breeding grounds. Females showed conflicting results: while testosterone production capability was higher than naturally circulating levels in individuals at both locations, those sampled farther from the breeding grounds showed a higher capability compared to those sampled closer to the breeding grounds. We are currently exploring the possibility that the proportion of testosterone that is converted to estradiol may change throughout migration.
