The effects of testosterone propionate and gonadotropins on the bill pigmentation and testes of the house sparrow ( Passer domesticus)

Abstract

Sexually regressed winter house sparrows, Passer domesticus, were treated with exogenous testosterone propionate, luteinizing hormone (LH) or follicle-stimulating hormone (FSH) after first confirming they were no longer photorefractory. Controls at the start and end of the experiment in December had the pale brown beaks typically noted in this species during the early winter. Treatment with relatively large doses of exogenous androgen did not cause the bill to assume a darker coloration than would occur in the wild in early spring. Neither FSH nor LH given alone restored pigmentation. A combination of FSH and LH caused a complete darkening of the bill, and FSH injected in combination with testosterone propionate was also effective. Testosterone propionate exerted a spermatokinetic effect consistent with other reports in the literature. Testicular weight and spermatogenetic condition was most advanced in subjects given FSH plus LH injections.