Overlap of Breeding and Molting Schedules in a Collection of African Birds

Abstract

Many birds in northern temperate regions are known to have distinct and separate times of the year for breeding and for molt, but little information is available for tropical birds.Miller (1961) found a separation of molt and breeding in tropical Zonotrichia caper&s, and he also described an inverse correlation in time between nesting activity and molt in an equatorial South American cloud forest (Miller 1963).Moreau (1936Moreau ( , 1950) ) reported overlap of molt and gonadal activity in less than 10 per cent of a sample of birds collected in equatorial Africa.Exceptions noted by Moreau were Colius striatus among the nonpasserines and Turdoides jardinei among the songbirds.These species had large gonads both in the breeding season and at the time of molt.In none of these studies was each of the instances of overlapping schedules discussed.The degree of overlap of gonadal activity and molt in tropical birds is of interest mainly because, in temperate regions, the separation of these two events in the annual cycle is thought to indicate metabolic incompatability of synchronous molting and breeding.Both of these events increase the demands of birds on their energy resources.The separation in time suggests that birds are limited by the availability of food.Farner (1964) has noted that the scheduling of the events of the annual cycle may also reflect the dependence of each event on a different set of hormonal conditions, but such incompatabilities of physiological mechanisms are themselves likely products of selection for separation of the energyconsuming events of breeding and molting.In contrast to the temperate regions where these ideas have developed, tropical regions are sometimes regarded as stable in time with minimal seasonal fluctuations in the abundance of food.It might be thought that species not limited by food may therefore breed and molt at the same time of the year.A collection of 1050 specimens of 190 species of birds was made from 1965 to 1967 as part of a field study in Africa.The collection has been divided between the U.S.