Abstract
Little is known about Southern ground-hornbill (SGH) population ecology outside of large, formally protected areas where the largest declines in numbers have been recorded. The SGH has started re-colonising, establishing group territories and breeding successfully in the Limpopo Valley on the northern border of South Africa, following localised extinction from the 1950s to the 1970s. A group of SGH was monitored over a period of 14 months by means of radio telemetry across privately owned land in order to investigate their seasonal habitat movements in this semi-arid, predominantly livestock-based environment. We also investigated seasonal fluctuations in invertebrate prevalence, as an indication of food availability and its influence on seasonal SGH group movements and foraging activity patterns. There was a clear increase in food availability during the summer rainfall period allowing the group to forage over a wider area, whilst winter foraging remained localised within their range. Kernel home range analysis indicated a marked difference in size between the summer (13 409 ha) and winter (5280 ha) home ranges, with an overall home range of 19 372 ha, which is approximately double that of home ranges recorded that fall within formally and informally protected reserves. In this article, we proposed that food availability is the driving force for home range size and seasonal activity patterns in a semi-arid livestock-ranching habitat.Conservation implications: The Limpopo Valley SGH population is one of the most significant outside protected areas in South Africa. This population is especially vulnerable to threats such as poisoning, persecution for window breaking and drought, as shown by their near extirpation from the area. Conservation efforts need to focus on awareness amongst local farmers, provision of artificial nests and continued monitoring of groups.
Highlights
The Southern ground-hornbill (SGH) (Bucorvus leadbeateri) is the largest hornbill in the world and the largest cooperatively breeding bird species (Kemp & Kemp 1980)
This study aims to investigate the seasonal availability of invertebrates in relation to rainfall, temperature and changes in vegetation cover and the possible consequence this may have on the habitat utilisation, movement and seasonal home range size of a group of SGH in the Limpopo Valley
Estimates of cover were very similar across all four sites (ANOVA: KW = 2.12, df = 3, p = 0.5470) and the average overall monthly score for all sites was very low at 17.7, representing an average cover of between 10.0% and 25.0%
Summary
The Southern ground-hornbill (SGH) (Bucorvus leadbeateri) is the largest hornbill in the world and the largest cooperatively breeding bird species (Kemp & Kemp 1980). It is a territorial, sedentary species and occurs in groups averaging 3–4 individuals consisting of an alpha pair and a mixture of juveniles and adult helpers (Kemp & Kemp 1980; Knight 1990). The species is officially listed as vulnerable in South Africa (Kemp 2000), whilst a recent review of the International Union for Conservation of Nature (IUCN) global status has precipitated a change in the species’ status from least concern to vulnerable by BirdLife International (2010). Suitability of habitat can be seen to contribute to the overall fitness and survival of an individual (Block & Brennan 1993) and the resources and conditions necessary to allow an organism to survive, reproduce and persist (Hall, Krausman & Morrison 1997)
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