Habitat use of Long-crested Eagles in human-modified landscapes of KwaZulu-Natal, South Africa.
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Date
2019
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Abstract
Loss of natural habitats due to land use change is threatening biodiversity globally, a cause for concern given the resulting loss of essential ecosystem services. Conservation of biodiversity within human-modified landscapes has become a necessity to halt further loss of biodiversity. The Long-crested Eagle Lophaetus occipitalis is an example of a species that can be managed within human-modified landscapes because it occurs in such landscapes, and the protection of its habitat may benefit other species that use the same habitats. The present study aimed to quantify the habitat use of Long-crested Eagles in human-modified landscapes of KwaZulu-Natal Province, South Africa, at various spatial scales and to make recommendations for the conservation of this species in such environments. Biodiversity in KwaZulu-Natal is threatened by anthropogenic activities that include agriculture, timber plantations and built environment.
Between August 2016 and September 2017, twelve Long-crested Eagle adults were tagged with geographic positioning system (GPS) transmitters in the KwaZulu-Natal Province. Telemetry data from the tagged eagles were used to estimate sizes of home ranges and habitat selection within home ranges. Home ranges of males and females were 420 ± 180 ha (n = 5) and 315 ± 161 ha (n = 4), respectively, using the kernel density estimator method (href 95%), and were not significantly different, suggesting similar ranging behaviour between sexes. The home range size of the eagles was relatively smaller than estimates reported from other parts of South Africa which may be an indication of high quality habitats for the species in KwaZulu-Natal Province. Home ranges in rural environments predominantly comprised of cropland (33%) and savanna (22%), whereas in suburban environments they comprised of settlements (34%) and exotic tree plantations (23%). In rural and suburban landscapes, the eagles positively selected for natural patches such as wetlands, natural forest, natural forest edge and savanna but avoided exotic tree plantations. Long-crested Eagles nested and roosted in the natural forests available within their home ranges.
Road surveys were used to determine land cover variables associated with Long-crested Eagle site occupancy at the landscape scale. ‘Cropland’ was the only land cover variable associated with occupancy and was positively associated with the area of cropland (β = 4.71 ± 2.28). Such results suggest that the apparent increase in abundance of Long-crested Eagles may be partly attributed to increase in cropland area. Although the influence of natural habitats was not significant at the landscape scale, it is less likely that the eagles selected territories based on the amount of cropland alone because they also needed nesting sites in addition to foraging habitats. Overall, Long-crested Eagles appear to be using edges of cultivated fields that have natural vegetation and hunting perches, and thus gaining improved access to prey. Natural patches of habitat add to the heterogeneity of agricultural landscapes making them more suitable for this species, as supported by the habitat preference observed within home ranges results. Wildlife friendly management of farms whereby natural habitats are retained appears to benefit Long-crested Eagles in agricultural landscapes.
Admission records from a specialist raptor rehabilitation centre in Pietermaritzburg were examined to identify common threats facing raptors in KwaZulu-Natal and determine factors that could be used to predict the outcome of rehabilitation. The major causes of admission to the rehabilitation centre were collision related injuries (52.1%), grounded birds (11.6%) and orphaned chicks (9.5%). Only the variable ‘reason for admission’ was a significant predictor of the outcome of rehabilitation. Raptors with no severe injuries such as orphaned chicks and grounded birds were more likely to have successful rehabilitation treatment than raptors suffering from collision injuries. In cases where triage is necessary, rehabilitation centres can make such decisions based on the nature of the injuries as this study has demonstrated that birds suffering from collision injuries were less likely to have successful rehabilitation.
In the wake of rapidly changing environments, conservation of biodiversity should not be left to protected areas alone, instead people should work together to make human-modified landscapes more habitable to wildlife. The presence of Long-crested Eagles on private properties should be an inspiration to do more to conserve wildlife.
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Doctoral Degree. University of KwaZulu-Natal, Pietermaritzburg.