Distribution of cavity-nesting birds and their potential nesting-sites in a tropical urban forest fragment

Populations of bird species that use cavities and are not excavators, are often limited by the availability of nesting sites. Undisturbed oldgrowth forests have high abundance and richness of species that use cavities because they harbor a larger proportion of large live trees and dead standing trees (snags). These trees are a notable source of nesting-sites for cavity-nesting birds, and therefore, their abundance is often a good surrogate for the availability of potential nesting sites. The goal of this study was to describe in an urban forest fragment of ca. 700 ha, how large-live trees, large-live palm trees and snags are distributed in relation to the edge of the forest fragment and also determine if the richness and abundance of cavity-nesting birds is related to the presence of these resources. We conducted this study in the forest fragment of the Federal University of Amazonas campus, in Manaus, Brazil. We established 20 transects of 120 m each (distributed 30 – 500 m from the forest edge) where we captured birds using mist-nets and counted the trees. We found no relation between the number of large-live trees, large-live palms and snags with the distance to the fragments edge. However, the richness and abundance of cavity-nesting bird species is higher in sites with the highest number of snags. These results reaffirm the great ecological value of snags and demonstrate their importance for the persistence of cavity-nesting bird populations in urban forests.