Long term prospects for the persistence of breeding Verreaux's Eagles (Aquila verreauxii) at the Walter Sisulu National Botanical Garden, Johannesburg

• Main Author: Kruger, Tamara Lauren
• Format: Others
• Language: en
• Published: 2010
• Online Access: http://hdl.handle.net/10539/8616

ABSTRACT Verreaux‟s Eagles (Aquila verreauxii) have been sighted in the Walter Sisulu National Botanical Garden since the 1940s. The natural habitat surrounding the Botanical Garden, which is utilised for hunting purposes, has undergone extensive urbanisation and subsequently the habitat required by typical prey species, such as Rock Hyrax (Procavia capensis), has decreased. As a result food supplementation during the breeding season was initiated by the Black Eagle Project Roodekrans (BEPR); a non-profit organisation dedicated to the preservation of these urban raptors. With further proposed urban development, the aim of this research was to deduce the long term prospects for breeding Verreaux‟s Eagles at the Botanical Garden. Analyses were carried out on historical aerial photographs to illustrate the decreasing natural habitat available for prey species within a 10 km radius of the eagle‟s nest site. The feeding data collected by the BEPR over a 16 year period (1993 - 2008) were analysed to investigate changes in prey species and breeding data were analysed to detect possible changes in breeding success over the 16 year period. The aerial photograph analysis indicated that prey suitable habitat within a 10 km radius of the nest diminished by approximately 29.7 km2 (9.5 %) from 1984 to 2007. In 2007 approximately 116.7 km2 (37.2 %) of suitable prey habitat remained within this radius, with a further reduction predicted to decrease suitable habitat within this radius, in the following three years, by an additional 1.03 km2 (1.3 %). The feeding data suggested that there has been a switch from Rock Hyrax to other prey species such as Helmeted Guineafowl (Numida melagris) and francolin (Francolinus spp.). The breeding data revealed few inconsistencies with respect to the incubation period, nestling period and post fledging dispersal period which were similar to established studies on Verreaux‟s Eagles. Despite a reduction in the suitable prey habitat and change in prey, breeding has persisted over the 16 year period. Therefore the prospects of these Verreaux‟s Eagles to continue to breed and hunt at the Botanical Gardens will depend on the, as yet unknown, threshold of prey abundance and habitat disturbance.