This project is aimed at better understanding the ecology and conservation of Martial Eagles Polemaetus bellicosus, with a particular focus on the declines observed within the country’s largest protected area, the Kruger National Park. This research aids our understanding of the role of protected areas for conserving wide-ranging species and the specific threats and habitat requirements of Martial Eagles.

This project was initiated in response to the decrease in reporting rates of Martial Eagles between the Southern African Bird Atlas Project, SABAP1 (1987-1992) and SABAP2 (2007-ongoing), which suggests a population decrease of up to 65% across South Africa. Declines were also observed inside large protected areas, such as the Kruger National Park (KNP), which experienced a 54% decrease in reporting rate. Similar decreases have been reported elsewhere in Africa resulting in the species being uplisted to ‘Endangered’ on the IUCN Red List. However, a new study, combining population trends from multiple African countries, suggests that declines across the entire African continent may warrant the species to be further uplisted to ‘Critically Endangered’ in the near future.

We aim to improve our understanding of the threats faced by Martial Eagles and how these threats may drive population decreases even within protected areas. 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 widely. Contrary to this hypothesis, we found little evidence for low survival during these early life stages, despite immature eagles ranging far beyond protected area boundaries. However, results from GPS tracking of adult birds and nest monitoring suggested two potential factors that may contribute to the observed population decreases: 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 population decreases.

Although our initial nest monitoring suggested low productivity rates, this may have been due to difficulties in detecting all nests of a pair. Indeed, using GPS tracking we have recently found that breeding performance may be better than initially thought and this shows the value of using tracking units to monitoring breeding performance in wide ranging species. For several years we have been placing cameras at nests to better understand the factors that influence prey provisioning rates and diet. These data have been used to understand how temperature can influence diet and nestling provisioning rates.

Although we are no longer actively monitoring nests on the ground in KNP, we are continuing to follow our tracked eagles to determine the frequency and causes of mortality, as well as the breeding status of our tracked birds to gain a more comprehensive understanding of the environmental drivers of breeding performance. Additionally, we have collaborated with the Endangered Wildlife Trust (EWT) on their project monitoring the Martial Eagles nesting on power pylons in the Karoo. This population may be the largest in South Africa, yet little is known about their productivity rates or survival, and whether this population may be acting as a source population for the rest of the region. Lastly, we have also been working on a movement model using tracking data from both the Kruger and Karoo populations to help inform wind farm development.

Activities in 2024

  • Kyle Walker submitted his MSc dissertation in Feb 2024. Kyle’s research explored how this species may respond as temperatures warm due to climate change. He investigated how provisioning rates of adults to their nestling change in hotter conditions, and whether diet flexibility may allow this species to adapt to rising temperatures. This analysis uses data from 12 camera traps that were placed at nests during the nestling period, and found dietary shifts in hotter conditions.
  • Building on the key findings from Kyle’s thesis, Dr Santiago Zuluaga (ABAX Foundation post-doctoral fellow) has been using data from our GPS tracked birds to explore whether dietary shift may be explained by changes in the movement patterns in hotter conditions.

Highlights

  • Kyle Walker graduated with Distinction for his MSc thesis on Martial Eagle food provisioning and diet in relation to temperature.
  • Arjun Amar was co-author on a paper published in Nature Ecology and Evolution which explored changes in raptors across African Savannas. This included the Martial Eagle which declined by over 90% over 3 generation lengths. These findings suggest that the IUCN status of this species may need to be reconsidered for uplisting to Critically Endangered.

Impact of the project
Our research provides a better foundation for protecting this Endangered species, within the most important areas for this species in South Africa.

Key co-supporters
ABAX Foundation; Endangered Wildlife Trust (EWT); SANParks; Eskom.

Research team 2024
Team leaders and collaborators:
A/Prof. Arjun Amar (FIAO, UCT)
Dr Megan Murgatroyd (HawkWatch International / EWT / FIAO, UCT)
Dr Santiago Zuluaga (ABAX Foundation post-doctoral fellow, FIAO, UCT)
Dr Chris Vennum (USGS)
Dr Gareth Tate (EWT)

Student:
Kyle Walker (MSc, UCT)