Tractrac Chat Emarginata tractrac: comparative biometrics, moult data and criteria for the determination of age and sex

Abstract

Data on the Tractrac Chat (Emarginata tractrac) (Wilkes), 1817 are scarce and widely scattered in the literature. We present measurement and moult data from 97 Tractrac Chats of the subspecies E. t. albicans ringed in Namibia over 20 years. We gathered published data of nesting, breeding and moulting, and compare our observations of the moult process and our records of active brood patches with breeding records compiled by Brown et al. (2017). On the basis of photographs, we describe the nestling of the ssp. E. t. albicans and its development to immature and then adult. We compare young and adult plumage and other features which help to distinguish these age groups. We also document several cases of irregular primary moult. We add observations on site fidelity; on changes in habitat and subsequent changes in numbers of territories; on the development of overall numbers of the species in our research area; on behaviour and on parasites and injuries. We also point out errata in the literature from Levaillant that remain in use, as well as discuss the elevation of the distribution range