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Current Research Programmes

Conserving Verreaux's Eagles

Verreaux’s Eagle Aquila verreauxi was uplisted to Vulnerable in South Africa in 2015. This project which aims to help conserve the species initially focused on investigating the impacts of land use change and habitat loss in the Western Cape, but now centres on reducing the impacts of wind farms because Verreaux’s Eagles are particularly vulnerable to colliding with wind turbines. The main goal is to be able to predict how the eagles use the landscape to prevent siting new turbines in risky locations for eagles.

Verreaux’s Eagle is generally regarded as a dietary specialist that mainly feeds on Rock Hyraxes Procavia capensis. As a result, habitat transformation that reduces the availability of its preferred prey species was expected to increase foraging effort and/or reduce breeding productivity. However, the initial research in this project found that Verreaux’s Eagles had more diverse diets in agriculturally developed areas and that breeding productivity was not affected by the levels of agricultural transformation currently experienced in the Sandveld region of the Western Cape.

The demand for renewable power is increasing worldwide and electricity generation from wind power is growing rapidly. In South Africa, at least 23 wind farms are operational and hundreds more are planned. Although wind energy is often regarded as a sustainable energy source, there are negative impacts on birds through collisions with rotor blades (see also the “Impacts of power infrastructure” p. 27). Diurnal raptors are the most frequently killed bird group, representing around 35% of casualties. This disproportionate effect on raptors is extremely worrying and we are working towards predictive collision risk models for the most susceptible species.

At least 14 adult Verreaux’s Eagles had been killed by turbines at South African wind energy facilities by the end of 2019. To help reduce further mortalities, we have built a predictive mapping tool using high-resolution GPS tracking data from adult eagles to understand flight behaviour, habitat use and the associated risk of wind turbine collisions. The resultant model is now being used by the wind energy industry to obtain collision risk maps of potential development areas early in the planning stage, thereby ensuring that wind turbines can be placed in locations that will minimise risk to eagles.

Activities in 2020

  • Fieldwork included ongoing monitoring of GPS-tagged eagles in the Karoo, Overberg and West Coast areas. Due to the large volume of data generated by the tags (over 1,000,000 fixes per year) data downloads are done via base stations rather than via satellite, which requires frequent maintenance of remote field equipment.
  • The collision risk model was used to assess risk profiles for turbines at 13 proposed wind energy developments in South Africa.
  • CB MSc student Merlyn Nkomo is analysing long-term Verreaux’s Eagle data from the Matapos Hills, Zimbabwe, supervised by Arjun Amar and Megan Murgatroyd. Her project explores the influence of weather on breeding performance. She will submit her thesis in March 2021.

Highlights:

  • A paper describing the methods for building the collision risk model was published in the Journal of Applied Ecology.
  • Megan Murgatroyd and Arjun Amar wrote a popular article in The Conversation “Finding space for both wind farms and eagles in South Africa”.

Impact of the project

This project has added to our understanding of the ecology and habitat requirements of Verreaux’s Eagles. The risk model to reduce mortalities due to wind turbine collisions will contribute to the long-term sustainability of wind energy development within Sub-Saharan Africa.

Key co-supporters

ABAX Foundation; DSI-NRF CoE grant; BirdLife South Africa; Birdlife Zimbabwe; Hawk Mountain Sanctuary; Mainstream Renewables; Avisense Consulting; Tygerberg Bird Club.

Research team 2020

A/Prof. Arjun Amar (FIAO, UCT)
Dr Megan Murgatroyd (HawkWatch International / EWT / FIAO, UCT)

Student: Merlyn Nkomo (CB MSc, UCT).