Selection of Nest Trees by Cavity-nesting Birds in the Neotropical Atlantic Forest

Abstract

One of the five most important global biodiversity hotspots, the Neotropical Atlantic forest supports a diverse community of birds that nest in tree cavities. Cavitynesting birds may be particularly sensitive to forestry and agricultural practices that remove potential nest trees; however, there have been few efforts to determine what constitutes a potential nest tree in Neotropical forests. We aimed to determine the characteristics of trees and cavities used in nesting by excavators (species that excavate their own nest cavity) and secondary cavity-nesters (species that rely on existing cavities), and to identify the characteristics of trees most likely to contain suitable cavities in the Atlantic forest of Argentina. We used univariate analyses and conditional logistic regression models to compare characteristics of nest trees paired with unused trees found over three breeding seasons (2006‐2008). Excavators selected dead or unhealthy trees. Secondary cavity-nesters primarily selected cavities that were deep and high on the tree, using live and dead cavity-bearing trees in proportion to their availability. Nonexcavated cavities suitable for birds occurred primarily in live trees. They were most likely to develop in large-diameter trees, especially grapiaApuleia leiocarpaand trees in co-dominant or suppressed crown classes. To conserve cavity-nesting birds of the Atlantic forest, we recommend a combination of policies, economic assistance, environmental education, and technical support for forest managers and small-scale farmers, to maintain large healthy and unhealthy trees in commercial logging operations and on farms.