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African Birds (african + bird)
Selected AbstractsFruit Traits in Baboon Diet: A Comparison with Plant Species Characteristics in West AfricaBIOTROPICA, Issue 3 2010Britta K. Kunz ABSTRACT Primate fruit choice among plant species has been attributed to different morphological plant and fruit characteristics. Despite a high abundance of animal-dispersed plant species in the savanna,forest mosaic of West Africa, few data are available on the interplay between morphological fruit traits and primate fruit consumers in this ecosystem. We tested whether olive baboons (Papio anubis) at Comoé National Park, north-eastern Ivory Coast, prefer fruit species with particular characteristics relative to the availability of these traits among the woody plant species at the study site. Specifically we were interested in the suites of traits that best predict fruit choice and seed handling by baboons. The baboons ate fruit/seeds from 74 identified plant species, representing 25 percent of the regional pool of woody plant species. They preferred trees to shrubs and lianas as fruit sources. Otherwise, baboons seemed to consume whatever fruit type, color, and size of fruit and seeds available, though they especially included larger fruit into their diet. Against expectations from the African bird,monkey fruit syndrome of brightly colored drupes and berries, baboons ate mostly species having large, dull-colored fruit. Fruit type and color best described whether baboons included a species into their diet, whereas fruit type and seed size best predicted whether baboons predated upon the seeds of their food plant species. As most plant species at the study site had medium-sized to large fruits and seeds, large frugivores like baboons might be particularly important for plant fitness and plant community dynamics in West African savanna,forest ecosystems. Abstract in French is available at http://www.blackwell-synergy.com/loi/btp [source] The implications of different species concepts for describing biodiversity patterns and assessing conservation needs for African birdsECOGRAPHY, Issue 5 2005Shaun Dillon It has been suggested that switching from the widely used Biological Species Concept to a Phylogenetic Species Concept, would result in the appearance of hitherto neglected patterns of endemism. The problem has mainly been analyzed with respect to endemic taxa and for rather limited geographical regions, but will here be analysed for the entire resident avifauna of sub-Saharan Africa. A database of African bird distributions was re-edited to create two new datasets representing 1572 biological species and 2098 phylogenetic species. Species richness patterns were virtually identical with the two taxonomies, and only subtle changes were found in the geographical variation in range-size rarity sum. However, there were some differences in the most range-restricted species, with increased complexity of long-recognized centres of endemism. Overall, then, the large-scale biogeographic patterns are robust to changes in species concepts. This reflects the aggregated nature of endemism, with certain areas acting as "species pumps" and large intervening areas being characterised by a predominance of widespread species which distribute themselves in accordance with contemporary environmental conditions. The percentages of phylogenetic and threatened species captured in a BSC near-minimum set of 64 grid-cells and a PSC near-maximum set, with the same number of grid-cells, are very similar. [source] Type and spatial structure of distribution data and the perceived determinants of geographical gradients in ecology: the species richness of African birdsGLOBAL ECOLOGY, Issue 5 2007Jana M. McPherson ABSTRACT Aim, Studies exploring the determinants of geographical gradients in the occurrence of species or their traits obtain data by: (1) overlaying species range maps; (2) mapping survey-based species counts; or (3) superimposing models of individual species' distributions. These data types have different spatial characteristics. We investigated whether these differences influence conclusions regarding postulated determinants of species richness patterns. Location, Our study examined terrestrial bird diversity patterns in 13 nations of southern and eastern Africa, spanning temperate to tropical climates. Methods, Four species richness maps were compiled based on range maps, field-derived bird atlas data, logistic and autologistic distribution models. Ordinary and spatial regression models served to examine how well each of five hypotheses predicted patterns in each map. These hypotheses propose productivity, temperature, the heat,water balance, habitat heterogeneity and climatic stability as the predominant determinants of species richness. Results, The four richness maps portrayed broadly similar geographical patterns but, due to the nature of underlying data types, exhibited marked differences in spatial autocorrelation structure. These differences in spatial structure emerged as important in determining which hypothesis appeared most capable of explaining each map's patterns. This was true even when regressions accounted for spurious effects of spatial autocorrelation. Each richness map, therefore, identified a different hypothesis as the most likely cause of broad-scale gradients in species diversity. Main conclusions, Because the ,true' spatial structure of species richness patterns remains elusive, firm conclusions regarding their underlying environmental drivers remain difficult. More broadly, our findings suggest that care should be taken to interpret putative determinants of large-scale ecological gradients in light of the type and spatial characteristics of the underlying data. Indeed, closer scrutiny of these underlying data , here the distributions of individual species , and their environmental associations may offer important insights into the ultimate causes of observed broad-scale patterns. [source] Range expansion of the globally Vulnerable Karamoja apalis Apalis karamojae in the Serengeti ecosystemAFRICAN JOURNAL OF ECOLOGY, Issue 3 2010Philip Shaw Abstract The underlying causes of change in geographic range size are less well understood in African birds than in north temperate species. Here, we examine factors associated with range expansion in the Karamoja apalis (Apalis karamojae), a globally Vulnerable warbler confined to north-east Uganda, north-central Tanzania and southern Kenya. In Tanzania, it was originally known only from the Wembere Steppe, but since 1993 (and possibly as early as 1983) has extended its range into the Serengeti ecosystem, c. 140 km to the north, reaching southern Kenya by 2004. Changes in the warbler's range within the Serengeti have broadly reflected a cyclical change in the density of its main habitat, Acacia drepanolobium woodland, which was low in the 1970s, high during the 1980s and 1990s, and declined in the early 2000s. Karamoja apalis records in the Serengeti showed a 5 year time lag behind A. drepanolobium density, which was in turn negatively correlated with the area of grassland burnt 10 years earlier. Previous studies in the Serengeti have also linked Acacia regeneration to changes in grazing pressure, as increasing wildebeest (Connochaetes taurinus) numbers have reduced the volume of combustible material present, and hence the frequency of damaging ,hot burns'. We conclude that this globally threatened warbler appears to have benefited from changes in ungulate populations in the Serengeti, which have influenced burning intensity and hence tree regeneration. The warbler's range now appears to be declining, however, following a recent reduction in the density and annual survival of A. drepanolobium in the northern Serengeti. Résumé Les causes sous-jacentes du changement de la taille d'une distribution géographique sont moins bien connues pour les oiseaux africains que pour les espèces du nord tempéré. Nous examinons ici des facteurs liés à l'expansion de l'aire de répartition de l'apalis de Karamoja Apalis karamojae, un sylviidé classé comme Vulnérable au niveau mondial, confiné au NE de l'Ouganda, au centre-nord de la Tanzanie et au sud du Kenya. En Tanzanie, on ne le connaissait à l'origine que dans la steppe de Wembere mais depuis 1993, et peut-être même dès 1983, il a étendu son aire de répartition dans l'écosystème du Serengeti, environ 140 km plus au nord, et atteint le sud du Kenya en 2004. Les changements de l'aire de répartition de ce sylviidé dans le Serengeti reflètent largement un changement cyclique de la densité de son habitat principal, la forêt d'Acacia drepanolobium, qui était faible dans les années 1970, forte pendant les années 1980 et 1990, et qui a diminué au début des années 2000. Les rapports sur l'apalis de Karamoja au Serengeti montrent un retard de cinq ans par rapport à l'évolution de la densité d'A. drepanolobium, elle-même étant négativement liée à la zone de prairie brûlée 10 ans plus tôt. Des études antérieures faites au Serengeti lient aussi la régénération des acacias aux changements de la pression du pâturage, étant donné que le nombre croissant de gnous, Connochaetes taurinus, a réduit le volume des matières combustibles restantes et donc la fréquence des feux trop chauds qui causent beaucoup de dégâts. Nous concluons que cet oiseau menacé au niveau mondial semble avoir bénéficié des changements des populations d'ongulés au Serengeti, qui ont influencé l'intensité des feux et donc la régénération des arbres. L'aire de répartition de ce sylviidé semble pourtant en train de se réduire suite à une récente réduction de la densité et de la survie annuelle d'A. drepanolobium dans le nord du Serengeti. [source] Impacts of Agriculture on the Diet and Productivity of Mackinder's Eagle Owls (Bubo capensis mackinderi ) in KenyaBIOTROPICA, Issue 4 2009Darcy L. Ogada ABSTRACT Land conversion for agriculture is an increasing threat to biodiversity conservation, but its ecological effects on African birds is practically unknown. We investigated the impacts of agriculture on the diet and productivity of a small, disjunct population of Mackinder's eagle owls (Bubo capensis mackinderi ) in central Kenya. Owl diet was determined by analysis of pellets and other remains and compared to small mammal populations estimated by live trapping in two habitats. Small mammal abundance was low and averaged 7.4 small mammals/ha in farms and 0.5 small mammals/ha in grassland. Owls consumed a wide diversity of prey. The majority were mammals (87%) followed by birds (7%) and insects (5%). The percentage of small mammals in owl diet correlated positively with the relative abundance of small mammals during monthly trapping sessions. Diet composition did not influence owl breeding success. Farming activities affected owl diet composition through crop production. The amount of maize, peas, and carrots growing in farms was correlated with the abundance of Mastomys sp. and Procavia sp. in the owl's diet. Agricultural activities had a large effect on Mackinder's eagle owl diet by increasing the abundance of certain small-mammal prey and attracting owl prey to farms, though farming practices harmful to owls were observed. [source] | ||||||||||