BIMODAL OCCURRENCE OF BREEDING IN AN EQUATORIAL SPARROW

Publisher Website
Google Scholar
Abstract
The continuous nesting of the Andean sparrow, Zonotrichia capensis, at the equator shows two peaks in frequency in the course of the year. The peaks are spaced at five- and seven-month intervals. The culminative phase of the breeding cycle, namely the production of fertile eggs, is more under the influence of environmental events than is the male cycle of reproductive potentiality and quiescence, which is largely innate. The asymmetrical spacing of the peaks of nesting within the year correlates with similar spacing of the wet and dry periods and especially with the two points each year when almost daily rains cease. No other environmental stimuli were found which correlate in a similar suggestive way. The most likely postulated mechanism for control of the nesting peaks involves the stimulus of the dry-out and sun exposure of the dry season to the onset of molt. The molt in turn reduces nesting because of a partial antagonism of this process and the culminative phase of breeding. Resumption of nesting at high frequency follows innate recovery processes of the adenohypophy-sisgonad mechanism and thus falls well within the rainy period subsequent to each dry period.

This publication has 1 reference indexed in Scilit: