Black Harriers Circus maurus breeding in the desert: new nest records from the Kalahari and Richtersveld, South Africa, coincide with a 1-in-25-year spike in greenness index

Abstract

Nomadic species such as the Endangered Black Harrier Circus maurus (family Accipitridae) exhibit rapid movements across country to locate suitable breeding areas within their breeding range in western and eastern regions of South Africa. Typically associated with the Cape Floral Kingdom and adjacent shrub-grass mosaics, breeding is associated with winter rainfall. However, when rainfall is sparse birds venture much further and this may take them to previously unrecorded locations. Here we document two breeding records, one observed directly, and one deduced remotely with GPS/GSM trackers, hundreds of kilometres north of all previous nest records in the arid Richtersveld and hyper-arid Kgalagadi Transfrontier Park of northwestern South Africa. The first occurred in an unnamed ephemeral riverbed in rocky upland terrain, and the second occurred between linear Kalahari dunes within 100 m of the ephemeral Nossob River. Both records occurred in September to November 2025, and both followed high rainfall events. On investigation we found a 1-in-25-year spike in primary productivity as gauged by the Normalised Deviation Vegetation Index and an abundance of mice in the Kalahari. These records show the remarkable ability of the Black Harrier to find and exploit transient productivity booms in arid landscapes that are typically unsuitable for nesting for decades at a time.