Range expansion of African Red-eyed Bulbul Pycnonotus nigricans in western South Africa

Abstract

Data from five citizen science projects were used to document shifting ranges of two species of bulbul in South Africa. We show that African Red-eyed Bulbuls Pycnonotus nigricans steadily replaced Cape Bulbuls P. capensis in the lower Olifants River valley, in northern Western Cape province, South Africa. The first observations of African Red-eyed Bulbuls in this valley were recorded by atlasers in winter 2011. Bird atlas reporting rates were still steadily increasing in this region at the end of 2021. Environmental conditions seem to have been suitable for range expansion of the African Red-eyed Bulbul into the area for at least five decades before they first arrived. This is a common feature of range expansions into the Western Cape. We discuss the value of the citizen science projects. The photographic records of the Virtual Museum have the advantage that they can be verified, and we made use of the habitat features displayed in the background. The bird atlas, in contrast, is based on sight records that cannot be checked; we observed a tendency for bird atlasers, who operate with fieldwork time constraints, to record the bulbuls in the study area as Cape Bulbuls because this was the bulbul that was traditionally observed there.