Availability of nest sites does not limit population size of southern flying squirrels

Abstract

Among factors that may limit population size, nest site is generally considered important for cavity-nesting species. We tested the hypothesis that nest-site availability limits population size in the southern flying squirrel (Glaucomys volans) by examining the effect of experimentally increasing the number of nest sites. We compared population sizes before and after adding 100 nest boxes (high-quality nests, increasing overall nest density by at least about 65%) on each of three experimental sites on the Savannah River Site in South Carolina. We also compared the experimental populations with three reference (unmanipulated) sites in a paired-block experimental design. All six populations were similarly monitored with livetrapping grids, and flying squirrels readily nested in the supplemental boxes. We predicted that population size would increase where nest sites were added. No increases in population size were observed after nest boxes were added to the three experimental sites, however, nor were populations higher on the experimental sites than on the reference sites. The lack of increase in population size after nest boxes were added demonstrates that the availability of nest sites was not limiting the size of these populations.