Includes bibliographical references. / Despite the importance of movement ecology studies, the field faces a prevailing challenge of methodological limitations in tracking individual organisms. This research investigated the utility of the stable isotope technique to trace movements of ducks in southern Africa. I sampled and analysed feathers of ten duck species for stable isotope proportions of Carbon (δ13C), Nitrogen (δ15N) and Hydrogen (δD), from five wetlands (Strandfontein and Barberspan in South Africa, the Manyame catchment in Zimbabwe, Lake Chuali in Mozambique, and Lake Ngami in Botswana) as test cases.Sampling was carried out at different seasons to account for seasonal isotope signature variations. Isotope signatures of feathers grown at different moulting locations were compared to test whether southern Africa shows stable isotope spatial patterns (distinct isotopic regions). Feathers grown at different life-phases were compared to test whether different sites had been used and if more mobile species showed more and stronger isotope distinctions. Finally, growing flight feathers grown at moulting locations were compared across species to query how much information on diet and foraging behaviour can be inferred from southern African duck feather stable isotopes.Feather isotope signatures were distinct by site in at least one of the tested isotopes, for the majority of ducks tested. Strandfontein had more and stronger distinctions of isotope signatures between feathers grown at different life phases. This site is the closest to the sea and most likely to have marine-influenced isotope signatures especially in δ15N, it falls within the Mediterranean climatic conditions experiencing winter rainfall unlike all the other sites. Vegetation compositions (C3 and C4 plant distributions) therefore vary across sites influencing δ13C patterns. More mobile species (only Egyptian Goose Alopochen aegyptiacus from Strandfontein, and Cape Shoveler Anas smithii from Barberspan; determined by mobility scores from other studies) had more and stronger distinctions between flight and body feathers. All the other species did not comply with mobility scores. They showed weaker and fewer tissue signature distinctions than their mobility scores suggested. There were high isotopic signature overlaps in δ13C and δ15N across and within feeding guilds at each moulting site implying dietary overlaps during moulting. More overlaps occurred during the dry seasons (summer in Strandfontein and winter in Lake Chuali, Manyame catchment site, and Lake Ngami). Higher isotopic variances (higher dietary flexibility) were associated with isotope signature divergence to mobility scores especially in Cape Teals and Yellow-billed Ducks.The isotope technique is flawed with uncontrollable sources of variation which potentially confound movement inferences. It is best used when accompanied by conventional methods to detect and counter against species specific biology and dietary behaviour imposed biases in tissue isotope signatures. Further research on how species specific biological processes affect the reflection of spatial patterns of isotopes in feathers is recommended. Multi-isotope time explicit approaches and trace element analysis were also recommended. Scientists should be wary about basing management strategies or building theory about movement patterns of species based on the technique at least in stochastic environments such as southern Africa. My results provide empirical evidence that the technique is unreliable at this scale of analysis. In particular, the majority of ducks in this region are not good candidates for use of isotopic signatures in distinguishing movement patterns of southern African ducks.4983
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uct/oai:localhost:11427/9801 |
| Date | January 2010 |
| Creators | Mutumi, Gregory Lilgee |
| Contributors | Cumming, Graeme S |
| Publisher | University of Cape Town, Faculty of Science, Department of Biological Sciences |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Master Thesis, Masters, MSc |
| Format | application/pdf |
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