Linkingfungi, trees, and hole-using birds in a Neotropical tree-cavity network: Pathways of cavity production and implications for conservation

COCKLE K; MARTIN K; ROBLEDO G.

FOREST ECOLOGY AND MANAGEMENT

ELSEVIER SCIENCE BV

Año: 2012 vol. 264 p. 210 - 219

0378-1127

In forests and savannahs worldwide, more than 1000 species of cavity-nesting vertebrates depend on the limited resource of cavities produced by avian excavators and decay processes in trees infected with heart-rot fungi. Conservation of cavity-nesting communities requires a solid understanding of how cavities are produced and used, yet no studies have examined the interactions among cavity producers and consumers in tropical forest, or the key role of heart-rot fungi for cavity-nesting vertebrates at a community level, anywhere in the world. We studied how interaction frequency was partitioned among network links between cavity producers (trees, heart-rot fungi, and avian excavators) and users (non-excavating birds) for a tropical cavity-nesting community in a region of high conservation concern, the South American Atlantic forest biodiversity hotspot. We identified two main pathways that produced the cavities used by non-excavators (secondary cavity-nesting birds). Thirty three percent of passerine nests and 9% of non-passerine nests were in cavities produced by avian excavators; the remaining nests (83% overall) were in cavities produced directly by decay processes (non-excavated cavities). Trees bearing cavities produced by excavators were 2/3 the diameter of those bearing non-excavated cavities, eight times more likely to be dead, and 37 times more likely to be colonized with heart-rot fungi in the family Polyporaceae s.l. (vs. Hymenochaetaceae). High diversity and evenness of network links suggest that this community should be relatively robust to random extinctions of cavity producing species; however, on-going destruction of large living trees with non-excavated cavities is likely to disrupt the major pathway of cavity production, and may result in a shift toward greater dependence on excavated cavities in smaller, dead trees, infected with Polyporaceae and occupied primarily by passerine birds.