STEVENSON, TJ; NORRAD, R; HAMPSON, E; MACDOUGALL-SHACKLETON, SA; Univ. of Western Ontario; Univ. of Western Ontario; Univ. of Western Ontario; Univ. of Western Ontario: Neural and endocrine response of female house sparrows to presence of conspecific males

Seasonally breeding songbirds exhibit large annual variation in reproductive physiology, the brain, and behavior. These changes are primarily driven by the annual change in day length, with other environmental and social cues modulating this photoperiod-driven response. We assessed how social cues affect central and peripheral reproductive physiology of female house sparrows, Passer domesticus. Female sparrows were housed in chambers either with other females or within view of testosterone treated males. Birds were kept on a short-day photoperiod for 40 days, then switched to long days for a further 21 days. We measured ovary size and plasma estradiol throughout the experiment, and measured GnRH-I and GnRH-II immunoreactivity in the hypothalamus at the end of the experiment. Transfer to long days significantly increased ovary size and plasma estradiol, however, there was no significant difference in either measure between females housed with males and females housed without males. There was also no difference in GnRH-I immunoreactivity between groups. GnRH-II immunoreactivity, however, was significantly greater in the septum,VMN and POA of females housed with males than in females not housed with males. Thus, although we could detect no effect of male presence on the gonads or gonadal hormones, male presence was associated with increased GnRH-II immunoreactivity in the hypothalamus. This result is consistent with the hypothesis that GnRH-II plays a functional role in the control of reproduction but does not have direct gonadotropic effects.