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

Standing dead trees (snags) are critical foraging and nesting sites fo r animals, notably birds, yet little is known about snag dynamics or c ommunities of cavity nesting birds in low latitude forests. In a compa rison among 10 New World forests, we observed that snags in tropical a nd 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 diamet ers (27.6-34.2 cm versus 11.2-31.2 cm) than snags in temperate and bor eal forests (N = 5 sites). No latitudinal trends were evident in avera ge density of live stems or average snag height. An analysis of avifau nal lists from these sites indicated that low latitude forests support ed 2.5 times as many cavity nesting species and approximately equal nu mbers of primary cavity excavating species as high latitude forests. I f tropical forests have fewer snags, more cavity nesters, and relative ly fewer cavity excavating species than temperate forests, limitations on nest-site availability could be more severe in lower than higher l atitude forests. The availability of snags for birds should thus be co nsidered by tropical forest managers, as it is by many temperate fores t managers.