Relationship between Species Richness of Excavator Birds and Cavity–adopters in Seven Tropical Forests in Costa Rica

The abundance of wood cavities is thought to be a limiting factor for bird species that depend on these cavities for nesting. Thus, it is expected that number of cavity adopters correlates with number of cavity excavators across communities. We used available published data to compare composition and richness of cavity adopters and cavity excavators across seven forest localities in Costa Rica. Species richness and composition of cavity excavator and cavity adopter bird assemblages varied among the seven forests. Species composition of excavators and adopters was more similar between nearby localities and between localities with similar forest types. Richness of wood-cavity adopters (using mostly cavities created by excavators) tended to increase with richness of excavators. The lack of association between cavity adopters and cavity excavators in some localities may be compensated by high abundance of a few species of excavators. The abundance of adopters and their dependence on forested habitats and on cavities excavated by woodpeckers varied largely across localities.