SNAG AVAILABILITY AND COMMUNITIES OF CAVITY-NESTING BIRDS IN TROPICAL VERSUS TEMPERATE FORESTS

Standing dead trees (snags) are critical foraging and nesting sites for animals, notably birds, yet little is known about snag dynamics or communities of cavity nesting birds in low latitude forests. In a comparison among 10 New World forests, we observed that snags in tropical and subtropical forests (N = 5 sites) occurred at lower densities (3.5-20.5 snags/ha versus 21.2-49.3 snags/ha) and had larger average diameters (27.6-34.2 cm versus 11.2-31.2 cm) than snags in temperate and boreal forests (N = 5 sites). No latitudinal trends were evident in average density of live stems or average snag height. An analysis of avifaunal lists from these sites indicated that low latitude forests supported 2.5 times as many cavity nesting species and approximately equal numbers of primary cavity excavating species as high latitude forests. If tropical forests have fewer snags, more cavity nesters, and relatively fewer cavity excavating species than temperate forests, limitations on nest-site availability could be more severe in lower than higher latitude forests. The availability of snags for birds should thus be considered by tropical forest managers, as it is by many temperate forest managers.