Conserving Verreaux's Eagles
In 2015 the conservation status of Verreaux’s Eagle Aquila verreauxii in southern Africa was changed from Least Concern to Vulnerable due to decreases in range and abundance recorded by the South African Bird Atlas Project. Our project on this species initially focused on investigating the potential impacts of land use change and habitat loss in the Western Cape. Generally regarded as a highly specialised raptor, habitat transformation was predicted to reduce availability of its preferred prey species, the Rock Hyrax Procavia capensis, resulting in reduced breeding productivity or increased foraging effort. Contrary to this prediction, we 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. A more recent and national threat is the development of wind turbine farms, and efforts have now shifted toward modelling the potential impacts of wind energy developments on this species.
The demand for renewable power is increasing worldwide and the installed electricity generation from wind power is growing rapidly. In South Africa, wind energy has grown at a rapid rate, with over 1 100 wind turbines becoming operational in the past five years and this trend can be expected to continue to rise rapidly. Wind energy is often regarded as a sustainable solution to our increasing energy demands. However, there are negative impacts on birds through collisions with rotor blades. In South Africa, post construction monitoring has found that diurnal raptors are the most frequently killed bird guild, representing around 35% of all casualties recorded. This disproportionate effect on raptors is extremely worrying and we are working towards predictive collision risk models for the most at risk species. Verreaux’s Eagles are highly susceptible to collisions, with mortalities recorded at several wind energy facilities. We have built a predictive mapping tool to enable turbine placement to occur in areas that minimise the risk of collision for this species. This used high-resolution GPS tracking technology to understand flight behaviour, habitat use and the associated risk of wind turbine collisions. The resultant collision risk 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 2019
- Fieldwork during 2019 included ongoing monitoring of the GPS tagged Verreaux’s 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 during 2019) data downloads are done via base stations (rather than via satellite), which requires frequent maintenance of remote field equipment.
- In 2019, we combined all the tracking data into a realistic collision model, which was then tested in its Beta form at a number of planned wind farm sites.
- We developed a collaboration with Merlyn Nkomo and BirdLife Zimbabwe, for Merlyn to analyse the long-running Verreaux Eagle data from the Matapos Hills first initiated by Valarie Gargett. This research will be undertaken by Merlyn for her Conservation Biology MSc thesis in 2020.
- The final version of the risk model, built using data from 16 tagged eagles, has been used at a number of wind farm sites, at the request of DEA, confirming the demand for such models.
- A paper describing the model has been submitted to the Journal of Applied Ecology and is currently in review.
- Dr Megan Murgatroyd was awarded the Leslie Brown memorial grant from the Raptor Research Foundation to track Verreaux’s Eagles in East Africa, in order to test the generalizability of our model in a different region.
- Megan fledged from the Fitz and secured a position as HawkWatch International's (HWI) first truly international conservation biologist. HWI work to conserve raptors and our shared environment and we now look forward to growing collaborations and continuing to work closely with Megan on this project.
Impact of the project
This project has added to our understanding of the ecology and habitat requirements of Verreaux’s Eagles. The primary aim of the ongoing work is to contribute to reducing future injuries and mortalities of Verreaux’s Eagles due to wind turbine collisions throughout their range. This will contribute to the long-term sustainability of wind energy development within Sub-Saharan Africa and minimise the impact on one of Africa’s most widespread and vulnerable eagle species.
ABAX Foundation; DST-NRF CoE grant; BirdLife South Africa; Hawk Mountain Sanctuary; Mainstream Renewables; Avisense Consulting; Tygerberg Bird Club
Dr Arjun Amar (FIAO, UCT)
Dr Megan Murgatroyd (FIAO, UCT)