Dispersal of young African black oystercatchers (Haematopus moquini): movement patterns, individual characteristics, habitat use and conservation implications

Rao, Anuradha Shakuntala (2005) Dispersal of young African black oystercatchers (Haematopus moquini): movement patterns, individual characteristics, habitat use and conservation implications. Masters thesis, Memorial University of Newfoundland.

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Abstract

The African Black Oystercatcher (Haematopus moquini) is a shorebird endemic to southern Africa, and is internationally listed as "Near-threatened''. Its population is increasing following protection measures and the invasion of the mussel Mytilus galloprovincialis. Although adults of the species are sedentary, dispersal up to 2800 km by immature birds was discovered in 1998. To ensure that conservation programs address the species' needs throughout its life cycle, this project determines the locations of importance to oystercatchers between the start and end points of their dispersal. -- Young African Black Oystercatchers disperse to a range of traditional locations along the coasts of South Africa and Namibia. Dispersal roosts along the Atlantic coast allow young birds to avoid competition for food with adults. Of the total number of South African-bred birds (n = 1 06) whose dispersal endpoints were confirmed, 65% dispersed to Namibia, 11% to north-western South Africa, 19% within south-western South Africa, and 5% dispersed along the south coast of South Africa. At least 22% of resighted birds departed in their first year of life, and 25% returned to the vicinity of their natal sites in their third or fourth year of life. At least 4% dispersed later than their first year. Body condition, sex and relative hatch date did not differ significantly between immature oystercatchers dispersing different distances. -- Roosts were mostly, but not exclusively, located in wave-sheltered areas containing both rocky and sandy substrata and with wide visibility angles allowing for vigilance against predators. The birds fed in the immediate vicinity of the roost sites at low tide. The largest roosts were in sheltered areas near river mouths; these sites were characterized by lower limpet numbers than smaller roosts. All but one roost checked also contained other shorebird and seabird species. -- Because these sites are traditional and used by several species for various purposes during a sensitive time of the oystercatchers' life cycle, they are important for conservation. However, several roost sites are located in areas zoned for diamond mining or development. Diamond mining can, at least temporarily, reduce the local abundance of oystercatcher prey, thereby eliminating the area as foraging habitat. Ribbon development on the coast should be discouraged to maintain undisturbed habitats, and coastal mining and mining-related activities should not be allowed in areas used by roosting or foraging shorebirds.

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