Dynamics of nest cavities in a Neotropical forest: key processes for creation and persistence

COCKLE, KRISTINA; MARTIN, KATHY

Halifax, Nova Scotia, Canada

Congreso; Meeting of the Canadian Society for Ecology and Evolution; 2009

Canadian Society for Ecology and Evolution

Globally, many species of forest birds depend on tree cavities for nesting and roosting. These birds interact in a nest web, whereby some species (excavators) or processes (decay, damage) create cavities, and others (secondary cavity nesters, SCN) depend on existing cavities. From 2006-2009, we studied a community of cavity nesting birds in the Atlantic forest of Misiones, Argentina, and located 125 nesting attempts of 30 species in 78 cavities. Whereas North American nest webs depend primarily on woodpecker holes in dead or dying trees, our nest web was strongly partitioned into two webs. Nest cavities created by decay in live branches or trunks (50%) were used sequentially by parrots, toucans and large woodcreepers. Cavities made by excavators were in dead branches or dead trees, and were infrequently reused, mostly by passerines. They were not avoided by SCNs but rather, often fell down before they could be reused. SCN selected cavities that were deeper, higher, less likely to have an upward-facing entrance, and in more isolated trees than unused cavities. The functioning of the main nest web depends on the supply of large, live trees where wood decay forms deep, long-lasting cavities high above the ground.