Seasonal variation in the vertical distribution of birds in the dry deciduous forest of central western Madagascar

The annual patterns of precipitation in the dry deciduous forest of Madagascar are characterized by a dry season when the majority of trees lose their leaves and a wet season with fill foliage development. Such variation allows the examination in shifts in the vertical distribution of birds and to their response to changing environmental conditions. Patterns of birds in the dry deciduous forest of Kirindy CNFEREF, central western Madagascar, were analyzed related to the vertical variation of vegetation structure and microclimate during 2 study periods: the dry (24 Aug to 16 Sep 2017) and wet seasons (25 Jan to 17 Feb 2018). Six line transects in forest habitat of 1,000 m each were used to survey birds, and each was associated with linear sampling to quantify vegetation structure. Data loggers were employed to record temperature and relative humidity across the vertical strata. During the dry season, associated with the microclimate aridity and reduction in vegetation cover in the upper strata, the number of species and individual birds found on the ground increased. During the wet season, fewer birds occurred on the ground, and abundance and species richness increased in the canopy. These results show the sensitivity of birds with regard to environmental fluctuations. However, regardless of the season, birds frequented mainly the mid-story, which had the highest abundance of species as compared to upper and lower vertical strata.