This discussion was first published as part of the 2016 Red List update. At the time a decision regarding its status was pended, but to enable potential reassessment of this species as part of the 2017 Red List update this post remained open and the date of posting was updated.
BirdLife species factsheet for Black Harrier: http://www.birdlife.org/datazone/species/factsheet/22695379
Circus maurus is found only in southern Africa, where it is concentrated in the Western Cape (its core range) in South Africa, and also occurs in the Eastern Cape, the Northern Cape and Free State in South Africa (R.E. Simmons in litt. 2004) with a population size of <1,000 individuals (Taylor et al. 2015). It is also found in Lesotho (non-breeding birds) (R.E. Simmons, O. Curtis and A. Jenkins in litt. 2004), with a tiny isolated population in northern Namibia (less than 50 birds including about five pairs [Simmons et al. 2015]). It is vagrant in Botswana and Swaziland (Hancock 2008). It is currently classified as globally Vulnerable on the basis of its small population size.
In the 2015 Eskom Red Data Book of Birds of South Africa, Lesotho and Swaziland (Taylor et al. 2015) this species is listed as Endangered, because of a very small population size which is likely declining, with the majority of individuals within one population. The Namibian Red List also classes the species as Endangered (Simmons et al. 2015), and Lee et al. (in press) state that the species has had a range decline of 41% since 1992 (36% decline in core range).
If these trends of decline are confirmed then this species would likely qualify for uplisting to Endangered under criterion C1+2a(ii), because there is a likely population size of <1,000 individuals which is undergoing a continuing decline of at least 20% over 2 generations, with 95-100% of individuals within one subpopulation. Any comments on the proposed uplisting are welcome.
Hancock, P. 2008. Black Harrier. In: Hancock, P. (ed.), The status of globally and nationally threatened birds in Botswana, 2008., pp. 13. BirdLife Botswana.
Lee, A.; Barnard, P.; Altwegg, R. (in press) Estimating conservation metrics from atlas data: the case of southern African endemic birds. Bird Conservation International.
Simmons, R. E.; Brown, C. J.; Kemper, J. 2015. Birds to watch in Namibia: red, rare and endemic species. Ministry of Environment and Tourism, Namibia Nature Foundation.
Taylor, M. R.; Peacock, F.; Wanless, R. M. 2015. The 2015 Eskom Red Data Book of Birds of South Africa, Lesotho and Swaziland. BirdLife South Africa, Johannesburg.