Site fidelity and longevity of the Karoo Thrush Turdus smithi (Bonaparte 1850) in an urban environment

Abstract

Turdus smithi, formerly a subspecies of T. olivaceus, has been elevated to species status, resulting in a void in our knowledge on this species. Although both T. smithi and T. olivaceus are common garden birds throughout their ranges, most studies to date have focused on T. olivaceus. These studies found that T. o. olivaceus reach ages in excess of 11 years and maintain territories of 10 000–13 000 m². The present study investigated site fidelity and longevity of an urban T. smithi population at the University of Pretoria main campus in Gauteng. Thrushes were ringed with unique colour ring combinations and identified by resighting them later. We found that T. smithi individuals have high site fidelity, with some thrushes being present in their same home ranges nearly nine years after being ringed, and suspect that they occupied these territories continuously between ringing and resighting. We found that T. smithi maintain larger home ranges than T. olivaceus individuals, and have a similar maximum longevity. We propose that adult thrushes are able to persist in a given home range because they are able to avoid resident predators, e.g. feral cats Felis sylvestris catus, by accurately predicting their hunting strategies.