White-crowned Shrike (Eurocephalus anguitimens) A. Smith, 1836: comparative biometrics, moult data and criteria for the determination of age

Abstract

We present measurement and moult data on the nominate subspecies of the White-crowned Shrike E. a. anguitimens from Namibia and South Africa and discuss plumage development through the different age groups. We compare our Namibian observations of the moult process and our records of active brood patches with breeding records (Brown et al. 2015) to gain a better understanding of the year’s cycle of the species. For South Africa, we show the progress of moult over the months, and note an overlap of moult and breeding in both Namibia and South Africa. We found three distinct plumages in the Southern White-crowned Shrike. Based on photographic evidence, we describe in detail the plumage development through the discernible age groups, from nestling to juvenile and immature to adult and describe criteria to determine a more exact age. We discuss variation in colouration and present observations on site fidelity, longevity and other aspects. This monograph is intended to supplement published data and encourage further discussion and research on plumage, moult and breeding, social structure and site fidelity