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During the year 1999-2001, avian assemblages associated with cliffs and bushy vegetation of the Clarens Formation have been quantified by means of the line transect method (total length of transects - 107 km) in Lesotho lowlands. In total, 80 species resident in these habitats were recorded. Overall, six species were classified as dominants: Serinus canicollis, Prinia maculosa, Streptopelia senegalensis, Emberiza tahapisi, Emberiza capensis and Cisticola fulvicapilla. Together they comprised 41.4 % of all breeding pairs. Ten other species were classified as subdominants (33.9 %). Granivores were the most numerous feeding guild (31 species; 48.0 % of all pairs), followed by insectivores (27 species; 32.3 %) and frugivores (11 species; 17.4 %). The most numerous nesting guild were shrub/tree nesting birds (47.2 %). Proportions for some congereric species were calculated. The bushy vegetation is characterized by high species diversity and relatively high population densities of some species.

Abstract

Temperature and rainfall related to altitudinal gradients influence ecological and evolutionary responses of organisms to physical factors. In this study, the line transect method was used during the years 1996–2001 to compare resident (potentially breeding) bird communities in three altitudinal divisions in Highveld/Drakensberg grasslands in Lesotho: lowlands (< 1700 m a. s. l.), foothills (1700–2200 m a. s. l.) and highlands (> 2200 m a. s. l.). In total, 105 resident species were recorded. The total number of species recorded in lowlands was higher than that in highlands and foothills, but this difference was not statistically significant. The highland and foothill did not differ in numbers of species. A group of five species dominated at all three sites, and the proportion of dominant species in relation to the whole assemblage was very similar. The composition of the dominant group (species with more than 5 % of pairs) and the group of species most often encountered (in more than 80 % of transects) was, however, different. Only two species, Cape Canary Serinuscanicollis and Karoo Prinia Priniamaculosa were dominant in all three study areas, and just one species, the Cape Bunting Emberizacapensis, was dominant in two plots. Similarly, only two species, the Cape Turtle-Dove Streptopelia capicola and Cape Canary had a high frequency of occurrence in all three study areas, and two otherspecies, theKaroo Prinia and Cape Bunting — in two study areas. Simpson’s Diversity Index was strikingly the same (S = 0.96) for all three avian assemblages (lowland, foothill and highland) investigated. However, proportions of breeding pairs of some congeneric species were found to change with the altitude. The granivores were more common (44–45 %) in the foothills and highlands than in lowlands (36%), while insectivores were more common in the highlands (50 %) than in foothills and lowlands (36–37 %). In general, avifauna is relatively diverse and unique in the Highveld/Drakensberg grasslands. Results presented here provide data for further investigation of the effect of the supposed climate warming on the diversity and structure of avian communities.