Browsing by Author "Klages, N T W"

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    Populations of surface-nesting seabirds at Marion Island, 1994/5-2002/3
    (2003) Crawford, R J M; Cooper, J; Dyer, B M; Greyling, M D; Klages, N T W; Ryan, P G; Petersen, S L; Underhill, L G; Upfold, L; Wilkinson, W; De Villiers, M S; Du Plessis, S; Du Toit, M; Leshoro, T M; Makhado, A B; Mason, M S; Merkle, D; Tshingana, D; Ward, V L; Whittington, P A
    During the 1990s and early 2000s, populations of surface-nesting seabirds at Marion Island showed different trends, but for the majority of species numbers decreased. Reduced numbers of gentoo penguins Pygoscelis papua, eastern rockhopper penguins Eudyptes chrysocome filholi, Crozet shags Phalacrocorax [atriceps] melanogenis and probably macaroni penguins E. chrysolophus are most plausibly attributed to an altered availability of food. Decreases in numbers of dark-mantled sooty albatrosses Phoebetria fusca, light-mantled sooty albatrosses P. palpebrata, southern giant petrels Macronectes giganteus and possibly northern giant petrels M. halli may have resulted from mortality of birds in longline fisheries. However, populations of wandering Diomedea exulans and grey-headed Thalassarche chrysostoma albatrosses fluctuated around a stable level. Numbers of Subantarctic skuas Catharacta antarctica and kelp gulls Larus dominicanus breeding at Marion Island also decreased. Kerguelen Sterna virgata and Antarctic S. vittata terns remain scarce at the island. Trends for king penguins Aptenodytes patagonicus were not reliably gauged, but numbers probably remained stable or increased. There were large fluctuations in numbers of king penguin chicks surviving to the end of winter.
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    Temporal variation of cephalods in the diet of Cape fur seals in Namibia
    (2003) De Bruyn, P J N; Bester, M N; Mecenero, S; Kirkman, S P; Roux, J-P; Klages, N T W
    Cape fur seal (Arctocephalus pusillus pusillus) scats were sampled over a period of eight years (1994–2001) at Atlas and Wolf Bay seal colonies in order to assess the cephalopod component of the diet of these seals and cephalopod diversity off the coast of Namibia. The temporal variation within the cephalopod component was investigated. A low diversity of cephalopods, only six species, are preyed upon, with Todarodes angolensis being the most important component both in numbers and wet weight in all years. Its lowered weight contribution during winter coincided with a greater diversity of other cephalopod species in the diet, which showed higher proportional weight contribution relative to Todarodes angolensis. Scat sampling was found to be an unreliable method of providing estimates of total prey weight consumption by seals, but was considered an acceptable method for proportional comparisons, especially given the ease of scat collection over extended periods.