The ecology of Black Sparrowhawks (Accipiter melanoleucus) in KwaZulu-Natal, South Africa.
Wreford, Erin Paula.
MetadataShow full item record
Black Sparrowhawks (Accipiter melanoleucus) are a medium-sized raptor found across much of sub-Saharan Africa. Within South Africa their distribution has historically been across most of the east with no distribution across the west of the country. Recently, however, the Black Sparrowhawks of South Africa appear to have undergone a range shift with their range expanding into the west, and in particular into the Cape Peninsula. Much of their new range appears to be into urban and peri-urban areas. The aim of this thesis was to analyse reproductive characteristics as well as range changes and dynamics of Black Sparrowhawks along a rural urban gradient in KwaZulu-Natal. In particular what influences range changes, reproductive success, nest site selection and home range of Black Sparrowhawks was determined. Urbanisation is one of the fastest changing and growing land uses worldwide, generally impacting negatively on fauna and flora community composition, species density and species ranges. Despite this the Black Sparrowhawk is one raptor species that appears to be thriving in urban habitats and has seemingly undergone recent range expansion, largely into urban areas. It was investigated whether Black Sparrowhawks have changed their range over recent years in South Africa. This was determined using data from both of the South African Bird Atlas Projects (SABAP1 and 2) and showed a definite shift and increase in the Black Sparrowhawk distribution. Black Sparrowhawk habitat use in terms of indigenous forest, commercial plantations and urban areas in South Africa were compared. Data from the SABAP2 project was analysed together with land cover types using generalized linear models with binomial errors and a logit link function. These results showed a positive relationship between the probability of encountering a Black Sparrowhawk in areas with tree plantations and in urban areas. However, no significant relationship was found between the probabilities of encountering a Black Sparrowhawk in areas of indigenous forest. Black Sparrowhawks appear to be a common urban species, however it seems they are limited to certain land use areas and this could affect their persistence in the future, particularly in urban areas. Black Sparrowhawks appear to be thriving in urban habitats. Typically known as a shy forest species, they are now frequently seen and heard in urban areas in South Africa during the breeding season. The spatial and environmental factors that influence Black Sparrowhawk nesting sites in urban and peri-urban areas were investigated in KwaZulu-Natal. Our data suggest that Black Sparrowhawks appear to be very selective in nest site selection particularly with respect to nest tree species, tree and nest height, area of greenspace’ surrounding the nest, and associations with water sources, roads and buildings. Black Sparrowhawks show a significant preference for a particular tree height class (20 – 29 m) as well as a significant preference for a specific nest height class (10 – 19 m). Similarly the preference of distance classes to the nearest water sources, buildings and roads all showed a significant selection by Black Sparrowhawks. Nest sites appear to be associated with the alien Eucalyptus sp. Due to ever changing urban habitats and human altered landscapes, as well as the removal of alien tree stands within urban areas, the availability of nest sites and foraging habitats may decline. It is therefore important that we understand the specific needs of such a species in order to monitor their success and initiate management programmes where necessary for their persistence. Black Sparrowhawks appear to be increasing in human altered landscapes, however little is known about their breeding success and characteristics. Consequently their reproductive and resource requirements and trends, as well as overall reproductive success along a rural/peri-urban urban gradient in KwaZulu-Natal were investigated. Over the 2011 and 2012 Black Sparrowhawk breeding seasons the majority of successful nests raised two nestlings. In 2011 Black Sparrowhawk nests had a success rate of 74 % while the success in 2012 was only 41 % which yielded a higher number of unsuccessful breeding attempts, these results were determined by nest observations during the breeding seasons. Nest preparation was done predominantly by the male with incubation then predominantly by the female. An increase in fresh leaf material being brought to the nest as the chick aged suggested that this is more likely due to parasite control rather than showing nest occupancy as has been previously speculated. There is little known about the movements and home range of Black Sparrowhawks, particularly in an urban environment. Consequently the home ranges of both an adult breeding female and a juvenile male Black Sparrowhawk were determined during the 2012 breeding season in Durban, KwaZulu-Natal. Transmitters were attached to the individuals recording their locations at regular intervals between 6h00 and 18h00. An adult female was trapped and had the transmitter placed approximately a week prior to the chicks fledging the nest. Her breeding season home range remained within close proximity to the nest. A juvenile male from the same nest was trapped approximately two weeks after fledging at the point of starting to learn to hunt independently. The data produced a minimum convex polygon (MCP) for the adult female of 0.0025 km2 while the young male remained within an MCP of 0.4554 km2. This pilot study has allowed us to determine a viable method which can be used to obtain Black Sparrowhawk home range information. This method can now be applied to numerous pairs within a population to determine home range overlap, territoriality as well as post natal dispersal. Despite the fact that Black Sparrowhawks appear to be increasing in human altered landscapes and expanding their range, further studies should be built on this pilot study in order to identify the degree of threat this species faces. This will allow for long term management plans to be establish which will facilitate their persistence in South Africa.