The standing dead: Importance of snags for cavity-nesting birds in tropical periurban forests

Forested periurban areas represent a major asset for conservation as these sites could potentially mitigate the effects of landscape modification. Nevertheless, these forests face unsupervised management, affecting availability of resources such as tree cavities used by cavity-nesting vertebrates. We evaluated the ecological importance of snags for cavity-nesting birds in 3 periurban cloud forest remnants with different management regimes, degree of protection, and size in Veracruz, Mexico. We compared snag and cavity availability, traits, and density of primary and secondary cavity-nesting birds in 3 forested sites with different sizes and degree of disturbance. We found no snags and low cavity density in the smaller fragments, as well as lower species richness and density of cavity-nesting birds. Most suitable cavities were excavated by woodpeckers in snags, and were located in the largest forest remnant, where we also recorded the highest abundance of snags, excavators, and the highest richness of secondary cavity-nesters. Our results suggest a synergy of snag availability, primary excavators, and richness of secondary cavity-nesters in cloud forest fragments. Furthermore, simple actions, such as snag removal and/or firewood extraction, which are common activities in smallforest fragments, can alter the composition of cavity-nesting assemblages with uncertain further ecological impacts.