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Investigating the effects of environmental variables on martial eagle breeding performance in the Kruger National Park
Within South Africa martial eagles reporting rates have decreased by almost 60% over the last two decades. Similar declines have also been reported within Kruger National Park (KNP), which is regarded as a stronghold for this species. Declines within KNP have been attributed to the low productivity...
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| Format: | Thesis |
| Language: | English |
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Department of Biological Sciences
2020
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| _version_ | 1867614410861707264 |
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| access_status_str | Open Access |
| author | Van Der Merwe, Daryl |
| author2 | Amar, Arjun |
| author_browse | Amar, Arjun Van Der Merwe, Daryl |
| author_facet | Amar, Arjun Van Der Merwe, Daryl |
| author_sort | Van Der Merwe, Daryl |
| collection | Thesis |
| description | Within South Africa martial eagles reporting rates have decreased by almost 60% over the last two decades. Similar declines have also been reported within Kruger National Park (KNP), which is regarded as a stronghold for this species. Declines within KNP have been attributed to the low productivity rates. As apex predators, marital eagles are considered to be good indicators of ecosystem health, being sensitive to the cumulative effects of disturbance down the food chain. Changes in the breeding performance of martial eagles may therefore indicate broader environmental change within the ecosystem. In this study, we aim to explore which environmental variables (e.g. climate, land cover, tree cover, fire and elephant abundance) within each territory correlated with martial eagle breeding performance in the hope that we may better understand which variables affect martial eagles breeding performance and whether these may have changed over time to cause the low levels of fecundity presently seen within KNP. We found that breeding productivity (young per territorial pair) was positively influenced by higher precipitation and Normalized Difference Vegetation Index (NDVI) and negatively impacted by high temperatures during the previous year. Breeding rate (breeding attempt per territorial pair) appeared to be negatively influenced by higher tree cover within 6 km of the nest site. Nesting success (outcome of a breeding attempt) was correlated with higher NDVI and lower relative levels of precipitation during the previous year. Using longer term climatic data and the relationship between climate in the previous year and productivity, (the variable which directly relates to annual fecundity), we hindcast the predicted productivity over the last three decades (2018-1986) to explore whether change in climate conditions (precipitation, temperature and NDVI) might reveal declines in productivity. No such declines were predicted, thus, our results do not explain why productivity has declined within KNP. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/31813 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:51:36.589Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2020 |
| publishDateRange | 2020 |
| publishDateSort | 2020 |
| publisher | Department of Biological Sciences |
| publisherStr | Department of Biological Sciences |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/31813 Investigating the effects of environmental variables on martial eagle breeding performance in the Kruger National Park Van Der Merwe, Daryl Amar, Arjun Murgatroyd, Megan Conservation Biology Within South Africa martial eagles reporting rates have decreased by almost 60% over the last two decades. Similar declines have also been reported within Kruger National Park (KNP), which is regarded as a stronghold for this species. Declines within KNP have been attributed to the low productivity rates. As apex predators, marital eagles are considered to be good indicators of ecosystem health, being sensitive to the cumulative effects of disturbance down the food chain. Changes in the breeding performance of martial eagles may therefore indicate broader environmental change within the ecosystem. In this study, we aim to explore which environmental variables (e.g. climate, land cover, tree cover, fire and elephant abundance) within each territory correlated with martial eagle breeding performance in the hope that we may better understand which variables affect martial eagles breeding performance and whether these may have changed over time to cause the low levels of fecundity presently seen within KNP. We found that breeding productivity (young per territorial pair) was positively influenced by higher precipitation and Normalized Difference Vegetation Index (NDVI) and negatively impacted by high temperatures during the previous year. Breeding rate (breeding attempt per territorial pair) appeared to be negatively influenced by higher tree cover within 6 km of the nest site. Nesting success (outcome of a breeding attempt) was correlated with higher NDVI and lower relative levels of precipitation during the previous year. Using longer term climatic data and the relationship between climate in the previous year and productivity, (the variable which directly relates to annual fecundity), we hindcast the predicted productivity over the last three decades (2018-1986) to explore whether change in climate conditions (precipitation, temperature and NDVI) might reveal declines in productivity. No such declines were predicted, thus, our results do not explain why productivity has declined within KNP. 2020-05-06T12:48:39Z 2020-05-06T12:48:39Z 2019 2020-05-06T01:38:44Z Master Thesis Masters MSc https://hdl.handle.net/11427/31813 eng application/pdf Department of Biological Sciences Faculty of Science |
| spellingShingle | Conservation Biology Van Der Merwe, Daryl Investigating the effects of environmental variables on martial eagle breeding performance in the Kruger National Park |
| thesis_degree_str | Master's |
| title | Investigating the effects of environmental variables on martial eagle breeding performance in the Kruger National Park |
| title_full | Investigating the effects of environmental variables on martial eagle breeding performance in the Kruger National Park |
| title_fullStr | Investigating the effects of environmental variables on martial eagle breeding performance in the Kruger National Park |
| title_full_unstemmed | Investigating the effects of environmental variables on martial eagle breeding performance in the Kruger National Park |
| title_short | Investigating the effects of environmental variables on martial eagle breeding performance in the Kruger National Park |
| title_sort | investigating the effects of environmental variables on martial eagle breeding performance in the kruger national park |
| topic | Conservation Biology |
| url | https://hdl.handle.net/11427/31813 |
| work_keys_str_mv | AT vandermerwedaryl investigatingtheeffectsofenvironmentalvariablesonmartialeaglebreedingperformanceinthekrugernationalpark |