Conserving Verreaux's Eagles
Verreaux’s Eagle Aquila verreauxii has recently been uplisted to Vulnerable in South Africa due to decreases in range and abundance recorded by the Southern African Bird Atlas Project. Land use change, habitat loss and more recently, the development of the wind energy industry, all pose threats to this species. Initially, this project explored the ecology of Verreaux’s Eagles in natural and agriculturally transformed habitats. 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 efforts. Contrary to this prediction, our research in the Cederberg and Sandveld regions of the Western Cape found that Verreaux’s Eagles are in fact diversifying their diet in agriculturally developed areas and their breeding productivity does not appear to be negatively impacted at the levels of agricultural transformation currently encountered by eagles in the Sandveld region.
The demand for renewable power is increasing worldwide and electricity generation from wind power is growing rapidly. In South Africa, there are currently 19 operational wind energy developments, with more than 600 turbines, producing 1.47 GW. The Department of Energy has committed to producing 13.23 GW of renewable energy generation by 2025. Although wind energy may be a sustainable solution to our increasing energy demands, it is not without its environmental impacts. Large raptors, particularly vultures and eagles are susceptible to turbine collisions, and to date in South Africa six Verreaux’s Eagle mortalities have been recorded. This project aims to build a predictive mapping tool for Verreaux’s Eagles to enable the placement of turbines in areas that will minimise the risk of collision for these eagles.
To do this we are using high-resolution GPS tracking technology to understand flight behaviour, habitat use and the associated risk of wind turbine collisions. Using GPS data from Verreaux’s Eagles we are building habitat use models that explore how territory holding eagles use the landscape. In particular, this will help us to understand how factors such as distance from the nest and topographical features influence their movements and the potential for wind turbine collisions. The aim is to incorporate these models within a user-friendly, web-based interface for use by the wind energy industry to obtain a collision risk map of any potential development areas early in the planning stage, thereby ensuring that wind turbines can be placed in locations that will minimise risk to flying eagles.
Activities in 2017
- Five Verreaux’s Eagles were fitted with high-resolution GPS tags. This brings our sample size of tagged eagles up to 16 individuals, which is deemed sufficient to build our predictive model.
- As habitat type, topography and eagle density might impact the likelihood of eagle collisions with wind turbines, we expanded our tagging activities into new areas. Understanding these impacts will be important for the national application of the final model.
- We continued data downloads from five eagles in the Karoo. These are now our longest running tags (1.5 years +) and these individuals all made a breeding attempt this year, indicating that these tags are not detrimental to the welfare of the birds.
- The first pair of Verreaux’s Eagles was tagged. Tracking data from both members of the same pair will allow us to assess if there is differential collision risk between the sexes and will give the first quantitative assessment of pair behaviour in this long-term monogamous species.
- The first version of the risk model built using a subset of data from six eagles, was applied on a local scale for a turbine development site in the Karoo. It indicated that the proposed development posed high risk to eight pairs of resident eagles.
- Presentations were given to the Endangered Wildlife Trust Birds of Prey programme, the Weskus Bewarings Kommitee, the Greater Cederberg Biodiversity Corridor Steering Committee, Tygerberg Bird Club, BLSA’s Vulture Working Group and the West Coast Bird Club.
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 will minimise the impact on one of the most widespread and vulnerable eagle species on the continent.
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)