Conserving Martial Eagles
The project aims to understand the factors driving a decrease in the population of Martial Eagles Polemaetus bellicosus in South Africa, with a particular focus on the declines observed within the largest protected area in the country, the Kruger National Park (KNP). This research is important to understand the role that protected areas have in species conservation and to understand specific threats and habitat requirements for the conservation of Martial Eagles.
The project was initiated in response to the decline in reporting rates of Martial Eagles between the Southern African Bird Atlas Projects (SABAP) 1 (1987–1992) and 2 (2007–2012). These surveys suggest population declines of up to 65% across South Africa. Declines were also observed inside large protected areas, such as the KNP, which experienced a 54% decline in reporting rate over this time.
We aim to improve our understanding of the threats faced by this species and how these threats may drive population declines even within protected areas, where species are usually expected to be conserved. Our original hypothesis for these declines was that Martial Eagles may be subject to increased mortality outside of protected areas, particularly during immature life stages when inexperienced eagles are likely to range outside protected areas. Contrary to this hypothesis, we have not found evidence for low survival during these early life stages despite ranging widely beyond protected area boundaries. However, through GPS tracking of adult birds and nest monitoring, two potential factors that may be contributing to the observed population declines have been detected: low adult survival and poor breeding productivity. Adult mortalities, including persecution and electrocution, during unexpected wide-ranging movements outside of the KNP, may be contributing to declines. The poor breeding productivity comes in two forms: both a lower than average number of pairs making a breeding attempt and low breeding success. We are continuing study the breeding performance of this species in the KNP to enable a more comprehensive understanding of the environmental drivers of poor breeding performance, as well as continuing to track eagles to determine the frequency and cause of mortalities.
Activities in 2019
- In 2019 we monitored 23 breeding territories which were considered to be occupied. Of these, there were only nine breeding attempts, of which three failed and six were successful. This equates to a breeding productivity of 0.26 young per pair, which is similar to previous years.
- Five nest cameras were installed: one nest was successful; two were regularly visited by eagles but not active; one was not useable due to a bad camera angle and at one the tree fell down (however we know from the camera that the nest was not being used this year by eagles).
- We commenced a collaboration with researchers from the Mara Raptor Project who have been studying Martial Eagles in Kenya since 2016. Using GPS transmitters, they have developed a method to rapidly identify kill locations and by visiting these sites they have uncovered detailed information on dietary requirements which differ between male and female eagles. A clear understanding of these requirements may help us to tease apart the drivers of poor success and to understand the conservation requirements of the species. The Mara Project has provided us with six of their GPS transmitters, of which two were deployed in 2019.
- Conservation Biology MSc student Rene Brink used data from this project as part of her thesis which examined whether circular buffers around nests adequately protect the ranging behaviours of raptors in Southern Africa.
- The first consecutive successful breeding attempt by a pair of Martial Eagles was recorded this year. The female of this nest was equipped with a microwave telemetry transmitter (sponsored by Jock’s Safari Lodge in 2018).
- A paper exploring the diet of Martial Eagles across their African range using photos sourced from the internet was published in the journal Condor. This collaborative paper involved several undergraduate and postgraduate students.
- Conservation Biology MSc student Daryl van der Merwe completed his MSc thesis. Daryl analysed all of the breeding data collected to date to explore which environmental factors were associated with variation in breeding success.
Impact of the project
Our research indicates that protected areas alone are unlikely to conserve this species and that additional conservation measures, such as education programmes, or trans-boundary policy should be put in place to ensure the successful conservation of this species.
ABAX Foundation; DST-NRF CoE grant; Endangered Wildlife Trust; Jock's Safari Lodge.
Research team 2019
A/Prof. Arjun Amar (FIAO, UCT)
Dr Megan Murgatroyd (HawkWatch International / EWT / FIAO, UCT)
John Davies (Endangered Wildlife Trust)
Dr Gareth Tate (Endangered Wildlife Trust)
Dr Lindy Thompson (Endangered Wildlife Trust)
Students: Rene Brink (CB MSc, UCT); Daryl van der Merwe (CB MSc, UCT).