Conserving the Black Harrier

Black Harriers (Circus maurus) are southern Africa’s rarest endemic raptor and have been uplisted from Vulnerable to Endangered in South Africa and Namibia in 2015. These top predators are a rare endemic to the southern African sub region with fewer than 1000 mature breeding birds left in the population. Studies have shown that there is little genetic variation across the population, indicating that this species is not in good shape and needs some serious conservation assistance going forward.

Ecology & Distribution

Ecology & Distribution

Black Harriers breed in the montane fynbos, renosterveld and strandveld habitats of the Western Cape and many individuals disperse into the karoo and grassland habitats during the autumn and winter months. The breeding success of Black Harriers is largely driven by winter rainfall in the Western Cape according to PhD student Marie-Sophie Garcia-Heras’ work at the Fitzpatrick Institute of African Ornithology at the University of Cape Town. Through the analysis of 400 nests over 15 years, her work has shown that the amount of rainfall which falls between April to September has a direct relationship with clutch size – more rain equals more eggs. Geographic location also influenced breeding behaviour with inland birds breeding over a shorter period than coastal birds. Inland harriers have a small window in which to breed and will thus lay larger clutches earlier in the season, however, this subpopulation has shown declines over time. Coastal birds, however, exploit the more benign weather conditions and feed on larger proportions of mice which allow them to produce more young over a longer period. The coastal population is believed to contribute the most number of new individuals to the overall population. The inland populations of Black Harriers have become increasingly fragmented through habitat loss and population declines and it is vital that conservation efforts invest in preventing fragmentation of coastal populations.

Threats

Threats

South Africa’s expanding agricultural sector has transformed vast areas of formerly natural habitat leading to habitat loss and fragmentation which threatens not only the Black Harrier, but also many other indigenous fauna and flora. Living in close proximity to these agricultural areas has resulted in high percentages of the population being exposed to chemical pollutants such as organochlorine pollutants (PCBs), DDT and its derivatives such as DDE. Blood samples of 90 nestlings and 23 adults indicated that 79% had persistent PCBs and 84% had evidence of DDT derivatives in their systems. Birds which fed in wetland areas and had a high percentage of birds in their diet had greater amounts of DDE in their bloodstreams. The majority of the nestlings with pollutants in their systems had higher white blood cell counts and compromised immune systems. Many of the chicks measured were raised in nature reserves indicating that the protected area network is unable to provide protection for the harriers. The use of DDT is banned in the Western Cape and the source of this pollutant measured in the harriers is unknown.
South Africa is currently rolling out new power producing technologies including wind turbines across parts of the Western Cape. Black Harriers now face a collision threat with wind turbine blades. If placed inappropriately, wind farm developments in southern Africa could result in significant harrier mortalities. Therefore there is an urgency to study the movements and behaviour of these raptors to inform power producers about high risk areas for Black Harriers.

Conservation & Research

Conservation & Research

The Black Harrier research team, affiliated with the FitzPatrick Institute of African Ornithology at the University of Cape Town, is the BirdLife Species Guardian for the Black Harrier under the global Preventing Extinctions Programme. Marie-Sophie’s PhD research is supervised by Dr Rob Simmons and by Dr Beatriz Arroyo and Dr François Mougeot of the Spanish National Research Council (CSIC). For more information, see updates at http://blackharrierspace.blogspot.com/ or contact Rob Simmons at rob.simmons@uct.ac.za or Marie-Sophie Garcia-Heras at ms.garciaheras@gmail.com

BirdLife South Africa has taken the results from Marie-Sophie’s PhD study relating to the observed correlation between the level of Polychlorinated biphenyls (PCBs) in the blood of Black Harrier chicks and their proximity to pole-mounted transformer boxes. PCBs are fall under the persistent organo-pollutants category and remain in the environment for extended periods. PCBs have been shown to cause negative physiological impacts on humans and wildlife across the world and were banned under the Stockholm Convention in 2004. An investigation to test this correlation is currently underway in collaboration with the Ingula Partnership. This will involve testing the soils around transformer boxes and Black Harrier nesting areas, as well as the transformer boxes themselves.

Find out more about the project

Species Research

Dr Rob Simmons (FitzPatrick Institute, University of Cape Town) is the Species Guardian for the Black Harrier and has many years of experience researching and supervising projects on the endemic Black Harrier.

For more information please email Rob.Simmons@uct.ac.za

Transformer Boxes and Black Harriers

Dr Melissa Whitecross (BirdLife South Africa) has been tasked with understanding the potential links between transformer boxes, PCBs and Black Harriers. This work is funded by the Ingula Partnership and is part of a broader collaboration with Eskom, EWT and BirdLife South Africa dubbed the Transformer Box Committee.

For more information please email melissa.whitecross@birdlife.org.za