Birds & Bats Unlimited



At Birds & Bats Unlimited we believe in solutions and much of our work aims to find ways to mitigate impacts of development.

Black Harriers and wind energy: guidelines

Black harrier and wind turbine

Black Harriers and wind energy: guidelines for impact assessment, monitoring and mitigation were published in 2020 by Rob Simmons of Birds & Bats Unlimited, with his colleagues S Ralston-Paton, R Colyn and MS Garcia-Heras.

As an Endangered species, with a very small global population and low genetic diversity, Black Harriers require concerted protection from all anthropogenic impacts. While collisions with wind turbines may be rare, harriers are not immune to this risk. Displaying, migrating and breeding harriers often fly at blade heights and therefore may collide with turbines. Black Harriers, especially breeding birds may also be negatively affected by disturbance associated with the construction, operation and maintenance of wind energy facilities (WEFs).

These guidelines present the most up to date research findings on Black Harriers, combined with contemporary overseas research on other harrier species and WEFs. Where data are limited, recommendations have been supplemented with expert opinion.

Areas where Black Harriers are likely to occur have been identified across South Africa and Lesotho. Without careful planning and management, the development of wind turbines within these areas may threaten their survival. These areas include:

  • the west coast (core breeding areas);
  • the Overberg (breeding and over-summer post-breeding areas);
  • the south-western Karoo and Nieuwoudtville areas (harriers breed in good rainfall years, and pass on migration);
  • the north-western coastal areas south of the Orange River (birds breed and pass through on migration);
  • ephemeral west flowing river (Buffels to Groen Rivier; birds breed);
  • Jeffreys Bay Kouga area of Eastern Cape (birds breed and roost communally);
  • the Central Karoo, de Aar region (birds stop over on migration);
  • grasslands of northern Free State (destination of migrant harriers);
  • Lesotho Highlands (destination of migrant harriers).

The decision tree in Figure 1 can be used to assist developers and specialists at critical stages in site screening and impact assessment.

Site screening should include habitat  suitability models for Black Harrier, SABAP1 and 2, BirdLasser, aerial photographs and Google Earth images. If this preliminary assessment indicates that Black Harriers are likely to occur in the area, we recommend that:

  • Vantage Point (VP) observations on WEFs are increased to 72 hours per vantage point per year, to reveal foraging areas, flight paths, migration corridors and/or nest sites;
  • Where proposed development sites fall within the breeding range of Black Harriers all suitable breeding habitat within at least 3-5 km of the proposed development footprint must be treated as focal sites and thoroughly surveyed for nests; a minimum of 4 hours monitoring (2 hours mid-morning and 2-hours mid-afternoon) must be undertaken during the start and end of the breeding season to watch for prey-carrying adults and other signs of breeding activity.

Within these areas, locations of high to very high sensitivity (potential critical habitat) should be identified during site screening and refined during impact assessment. These areas include:

  • Suitable breeding habitat,
  • Nest sites (buffered by 3-5km),
  • Potentially prime foraging (and breeding) habitat – (e.g. suitable Black Harrier habitat that has also been identified as a Protected Area, Critical Biodiversity Area (CBAs) or Ecological Support Area (ESA)),
  • Likely flight paths and high use areas around potential breeding and foraging sites, and
  • Roost sites, plus a buffer of at least 3-5 km for communal roosts, or 1-3 km for single roosts.

Development of wind turbines within these high to very high sensitivity areas is discouraged and a precautionary approach to development is  recommended. In other words, it must be clearly demonstrated through rigorous monitoring (i.e. at least two years of data collection, covering two breeding seasons) that the proposed development site is not in an area that is regularly used for breeding, roosting, foraging or migration. In particular, nest buffers (3-5 km) and roost buffers (3-5 km) and the avoidance of any suitable breeding habitat (as identified in the avifaunal assessment) is strongly recommended, even if no breeding or roosting activity is recorded during the monitoring period.

Sustainable development requires that the mitigation hierarchy be implemented; i.e. disturbance of ecosystems and loss of biological diversity are first avoided, or where they cannot be altogether avoided, are minimised and remedied. Where operational wind turbines present a residual risk to Black Harriers(i.e. once the mitigation hierarchy has been applied, impacts avoided, and/or minimised through appropriate site selection and design), or where fatalities are recorded during operational phase monitoring, one or more of the following mitigations must be implemented to reduce the risk of collisions through:

  • Implement curtailment or shutdown on demand;
  • Increase the visibility of turbines by painting one blade red or black;
  • Increase the distance between the lowest blade tip and the ground (in foraging habitat);
  • Attempt to draw harriers away from the site though the  improvement/rehabilitation of
    nearby habitat; and/or
  • Reduce the attractiveness of the habitat to harriers (e.g. mowing, burning or increased stocking rates to reduce prey populations).

While some of the above measures have been tested on other harriers, they remain untested on Black Harriers and should therefore be implemented as part of an adaptive management strategy. Some of these measures may also have negative effects (e.g. visual and/or ecological impacts) and these impacts should be assessed by the relevant specialists before they are implemented.