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Résumé
Zombitse and Vohibasia are situated 120km east of Toliara and are the largest of several forest fragments that form the southernmost tracts of dry forest in Madagascar. They have a combined area of about 750km2 and are entirely surrounded by a vast area of anthropogenic savanna. This report is the result of five weeks ornithological and sociological research.
Four sites were visited, each adjacent to villages and at different distances from Sakaraha (the main urban centre) and the Antananarivo to Toliara road. At each site, ornithological surveys were carried out on the nearest forest blocks using Point Transect methods to derive relative density estimates between the sites. This was only possible for common species. In addition, therefore, an analysis of forest importance was made using a biological scoring system. It is hoped that this baseline assessment of four sites in the new national park will promote further survey work in other areas of forest.
The results demonstrate how the bird communities and the abundance of species differs at each site. Areas of Vohibasia forest near Sihanamena (the most isolated village in the survey) support a relatively important bird community and levels of human threat currently seem sustainable. Appert's Greenbul was also found in Vohibasia forest, the first time since the type specimen was collected in 1962. Mangona, which lies adjacent to Sihanamena was heavily exploited for timber in the past and has a poor number of bird species, few of which are under threat in Madagascar. This small forest block continues to be the main source of timber for the Sihanamena villagers.
The remaining sites, in Zombitse forest, were both important in terms of threatened species, but the Ambiamena site supported a greater diversity of species than any other site we surveyed. Ambiamena comprises a mosaic of habitats including a rare fragment of gallery forest, standing water and wetland vegetation arising from the source of the Ambiamena river. Forest near the migrant village of Andranamaitso is next to the main road and supported the poorest diversity of bird species. However, like Ambiamena there were a number of threatened and near-threatened species. Appert's Greenbul was especially common which may suggest that the species is tolerant of some habitat degradation.
The ornithological site score for Ambiamena was highest at 55. Vohibasia and Andranamaitso each scored 53, but Mangona only scored 45. The degree of similarity between the three highest scoring sites is an indication that conservation initiatives should be spread evenly throughout the forests. The existing Integrated Conservation Development Project had to some extent failed to involve the more distant communities in negotiations for the new national park. This is perhaps an unfortunate result of lack of resources needed to reach some of the isolated villages on a regular basis. Nonetheless, it puts even greater emphasis on the need for a decentralised approach to integrate people and conservation in this unique remnant of dry forest.
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