Bird species diversity is generally higher in tropical forests than in temperate forests. This latitudinal gradient of species diversity has been mainly explained by external factors such as the structural complexity of habitat (MacArthur et al. 1966), climatic stability (Stiles 1978) and predictability or diversity of food resources (Karr 1971;Schoener 1971). In contrast, Powell (1989) explained the high species richness in the neotropical avifauna as arising from the internal structure of the community itself. Multispecies territoriality (i.e., the year-round communal defence of territory) by the core species of mixed-species flocks reduces the densities of small species because they have larger territories than expected from their body size. As a result, a greater number of small species can coexist owing to the under-utilization of food resources in such a community.Madagascar, which lies within the tropical region, supports various kinds of forests including: rain forest, deciduous broad-leaved forest, and subarid scrub.Although the avifauna is highly unique with Ͼ50% of the breeding species endemic (Langrand 1990), there have been no quantitative studies of Madagascan forest bird communities. Multispecies bird flocks are observed all year round in Madagascan forests (Eguchi et al. 1993;Hino 1998Hino , 2000 as well as in other tropical forests (Bell 1983;Powell 1989;Jullien & Thiollay 1998). Hino (1998Hino ( , 2000 has shown that the core species of mixed flocks in deciduous broadleaved forest in Madagascar gain mutual benefits relating to foraging and/or anti-predation. The deciduous forest is an appropriate habitat to examine the factors, other than foliage structure, that may explain the differences between bird communities in tropical and temperate forests. In this paper, I describe the characteristics of breeding bird communities in a deciduous broad-leaved forest in western Madagascar by comparing them with those of temperate forests in Japan. Then I consider the effect of predators and multispecies flocking to explain the characteristics of the Madagascan bird community.
Breeding bird community and mixed-species flocking in a deciduous broad-leaved forest in western MadagascarTeruaki HINO # Kansai Research Center, Forestry and Forest Products Research Institute, Japan Abstract The breeding bird population of a deciduous broadleaved forest in western 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 abundance of nest-predators such as large lizards and snakes in these areas. The bird community was dominated in abundance by the members of mixed-species flocks, almost all...