Conserving Martial Eagles
The Martial Eagle 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 that have been 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 into areas with increased human pressures. Contrary to this hypothesis, we have not found evidence for low survival duringthese 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 success of those pairs which do try. We are continuing to work towards a long-term dataset on the breeding performance of this species in the KNP to enable an understanding of the environmental drivers of poor breeding performance, as well as continuing to GPS track eagles to determine the frequency and cause of mortalities.
Activities in 2018
- In 2018 we monitored the breeding activity of 27 pairs of Martial Eagles in KNP. This included three new nests that were located (one via road surveys, one tourist reports and one found by SANParks staff). Monitoring of 12 territories was discontinued after the first check due to collapsed nests or fallen trees. With the help of EWT staff we were able to make four visits (rather than the usual three) to get the timing right for nest camera installations. The proportion of pairs that bred successfully in 2018 was found to be similar to the low breeding productivity recorded in previous years.
- We installed seven nest cameras to help understand the cause for breeding failure.
- A further two adult eagles were trapped – one was equipped with a GPS tracker and the other was fitted with an alphanumeric colour ring for re-sighting data. One chick was also fitted with an alphanumeric ring prior to fledging.
- CB MSc student Daryl van der Merwe joined the project. Under the supervision of Arjun Amar and Megan Murgatroyd, he is analysing all of the breeding data collected to date to explore if any environmental factors are associated with low breeding success.
- We presented our findings at the International Raptor Research Foundation congress at Skukuza.
- We published key research findings that quantified the overall decline of the species across South Africa in Bird Conservation International.
- One unusual nesting failure was recorded; a honey badger climbed to the nest and killed the incubating adult eagle and ate the egg. This unexpected finding would not have been detected without the use of nest cameras.
- We also explored the diet of Martial Eagles across their African range using photos sourced from the internet. This paper was accepted for publication in Condor and will be published in 2019.
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.
Dr Arjun Amar (FIAO, UCT)
Dr Megan Murgatroyd (FIAO, UCT)
John Davies (Endangered Wildlife Trust)
Dr Gareth Tate (FIAO, UCT, Endangered Wildlife Trust)
Dr Lindy Thompson (Endangered Wildlife Trust)
Student: Daryl van der Merwe (CB MSc, UCT).