Treefalls and the Distribution of Understory Birds in a Tropical Forest

Monthly mist—net censuses were conducted in central Panama to contrast the species richness and composition of the understory avifauna in treefall gaps to that of adjacent, intact forest. We compiled 826 captures of 73 species over a 9—mo period. Species richness was greater in gaps than forest (66 vs. 53 species), but capture rates were nearly identical (gap, 409; forest, 417). Of the 31 species with adequate sample sizes, 5 displayed significant habitat preference (P ° .05): 3 in gaps and 2 in forest. Ordination of all nets by Bray—Curtis analysis indicates that gap and forest bird assemblages are quite distinct. We suggest that treefall gaps contribute to the structural heterogeneity of the forest and influence the composition and richness of the bird community.