Meeting Abstract

79.6  Tuesday, Jan. 6  Changes in Reproductive Hormones with Age in the Florida Scrub-Jay (Aphelocoma coerulescens) WILCOXEN, T.E.*; SCHOECH, S.J.; BRIDGE, E.S.; BOUGHTON, R.K.; REYNOLDS, S.J.; University of Memphis; University of Memphis; Oklahoma Biol. Survey; Archbold Biological Station; Univ. of Birmingham, UK twilcoxn@memphis.edu

Analysis of fifteen years of data from our study population of Florida Scrub-Jays reveals a quadratic relationship between female breeder age and number of fledglings produced, with the youngest and oldest birds having the lowest reproductive success. A similar pattern holds for male breeders and fledgling production. In most vertebrates, production of reproductive hormones wanes with age, co-occurring with the decline in reproductive output. Measurement of these hormones can serve as a key marker of the onset of reproductive senescence. We collected blood samples from jays during the breeding season and used radioimmunoassay for luteinizing hormone (LH), estradiol (E₂), and testosterone (T). We hypothesized that concentrations of circulating reproductive hormones will change with age, and predicted declines in reproductive hormones with age in breeding jays. Samples were grouped according to the capture date in relation to the day the first egg was laid in the territory, and analyses were performed within each group to control for naturally occurring changes in circulating hormones during different stages of the breeding season. Male breeders LH and T concentrations follow a quadratic pattern, with low titers in young, maximum concentrations in middle aged, followed by a decline in plasma levels in the oldest birds. This distribution parallels the relationship between male breeder age and fledgling production, which mirrors the female pattern, and suggests that decreased T may reflect reproductive senescence. Interestingly, data for LH, E₂ and female breeder age reveals no age-based differences.