SMALL, TW; DEVICHE, P; SHARP, PJ; BENTLEY, GE; MILLAR, RP; TSUTSUI, K; Arizona State Univ; Arizona State Univ; Roslin Inst, Edinburgh, Scotland; Univ of Washington; Univ of Edinburgh, Scotland; Hiroshima Univ, Japan; ; : Supplementary information, not photoperiod, regulates plasma luteinizing hormone in male Rufous-winged Sparrows, Aimophila carpalis

In most passerines studied thus far, annual changes in day length control seasonal reproductive development and regression. Exposure to increasing photoperiod in the spring stimulates the release of luteinizing hormone (LH) and follicle-stimulating hormone, causing development of the reproductive system. However, birds living in less seasonal environments often time breeding based on environmental conditions that are not reliably predicted by photoperiod. We investigated the regulation of reproduction in male Rufous-winged Sparrows, a resident of the Sonoran desert that breeds after summer rains. We previously determined that free-living sparrows develop their testes in March due to increasing photoperiod and regress their gonads in September due to decreasing photoperiod and relative photorefractoriness. Plasma LH in free-ranging males does not increase in the spring, as in other birds, but correlates with precipitation. Further, day length never exceeds 15L in the wild, and plasma LH in captive males increased upon transfer from 8L:16D to 16L:8D but not to 13L:11D or 14L:10D. We conclude that plasma LH in free-living male Rufous-winged Sparrows is primarily under the control of supplementary information, and long photoperiods may augment the effect of this information. Immunocytochemical staining of brain sections from birds collected before and after the beginning of the monsoon rains for gonadotropin-releasing hormone (GnRH), ProGnRH (the GnRH precursor) and gonadotropin-inhibiting hormone (GnIH) suggests that increased plasma LH during the monsoon season may result from decreased GnIH and not increased GnRH release.