Sexual Cycles of Pigeons in a Tropical Environment.

Abstract

The sexual cycles of two genera of frugivorous rain-forest pigeons, Ducula and Ptilinopus, and two ground-feeding pigeons of the open woodland, Geopelia humeralis and G. striata, have been studied at latitude 9D 29'S. in New Guinea. In P, iozonus, P. magnificus, G. humevalis and G. striata some males were sexually active and some females had enlarged follicles in each month of the year and so some individuals, at all times, were capable of breeding; there was an indication that this situation was general in the two genera. In the rain-forest species more birds had enlarged gonads in the late dry season and wet season than at other times. Both sexes of G. stviata had peak gonad size in the late wet and early dry seasons; G. humevalis maintained peak activity throughout the dry season; both species had small gonads in the late dry season. The cycles of gonad size of fruit pigeons and ground-feeding pigeons corresponded to the probable cycle of food abundance in the two habitats. There was no evidence of an effect of photoperiod in Geopelia but it could not be excluded in males of Ptilinopus.