Vertical distribution of birds in différent dry forest types of western Madagascar (1st part)

Aspects associated with the vertical structure of naturel vegetation on bird richness, composition, diversity index and abundance, particularly for 13 common species, were examined at three lowland protected areas falling along a latitudinal gradient: dry deciduous forest of Ankarafantsika (north-west) and Kirindy CNFEREF (central-west) and dry spiny thicket of Tsimanampesotse (south-west). Observations were made during the dry season from May 2017 to September 2017 using linear transects to survey birds and linear sampling to quantify vegetation structure. Ankarafantsika and Kirindy showed similar patterns along different vertical strata, including species composition, and more specifically with the mid-story containing the highest bird species richness and abundance. The habitat structure of Tsimanampesotse differs from the two dry forest sites, being more open and lower in stature, with the canopy having the highest species richness and the Under-story the highest abundance. Both dry deciduous forest and spiny thicket habitats show similarities in bird species diversity index, which increases along a vertical gradient, with the upper strata having the highest values and an associated decrease in vegetation cover. The vertical distribution of the most common bird species (10 of 13) differed significantly between the different forest types. Vertical differences in the distribution of the bird communities can be explained by changes in vegetation structure, specific composition, bioclimatic conditions, resource availability, and différent ecological factors. This study provides a foundation for future ecological studies on forest-dwelling birds of western Madagascar.