Red-backed Shrike (Lanius collurio) Linnaeus, 1758 on its non-breeding grounds: comparative biometrics, moult data and criteria to determine age and sex

Abstract

Much is still unknown or unpublished in the Afrotropical literature concerning the complexity of the plumage features of the Red-backed Shrike (Lanius collurio). We present measurements, moult data and related observations for about 300 Red-backed Shrikes collected while ringing them in their non-breeding range in southern Africa. We discuss our findings on timing and progress of primary moult in adults and birds in their first year of life. We describe in detail plumage features for the determination of age and sex, and discuss colour and plumage variations in both sexes, especially females, and the occurrence of white wing patches in males. We give photographic evidence of the change of the bill colour during the non-breeding season and add notes on age and sex ratio, retraps and site fidelity. We also discuss the long-standing claims of Red-backed Shrike breeding in the southern hemisphere. Our field excursions between 2002 and 2022 were based mainly in Namibia during the Austral summer months, from November to April. We have included supplementary records of this species from Botswana and Zambia.