Breeding bird community and mixed-species flocking in a deciduous broad-leaved forest in western Madagascar

Abstract

The breeding bird population of a deciduous broadleaved forest in west- ern Madagascar was censused by means of territory mapping. Despite the foliage structure being simpler, neither species richness nor density was less than those in mature temperate forests. Species diversity was higher in the western Madagascan forest owing to the higher species evenness. Tree-cavity nesters and bark foragers were few because woodpeckers, nuthatches, and tits have not colonized Madagascar. The scarcity of birds nesting on or near the forest floor may be attributable to abun- dance of nest-predators such as large lizards and snakes in these areas. The bird com- munity was dominated in abundance by the members of mixed-species flocks, almost all of which forage in the canopy. Mixed-flocking can be beneficial for these birds to avoid predation by raptors, which were frequently observed in the canopy. Since most of the flock members had relatively similar territory sizes resulting in similar densi- ties, the high species evenness in this community may have resulted from mixed- flocking by canopy-foraging species.