Does the availability of artificial cavities affect cavity excavation rates in red-cockaded woodpeckers?
Rates of cavity excavation by Red-cockaded Woodpeckers (Picoides borealis) were examined from 1983 to 1999 on the Angelina National Forest in east Texas. We compared the rare of natural cavity excavation between 1983 and 1990 (before artificial cavities were available) with the rate of cavity excavation between 1992 and 1993, a period when artificial cavities were regularly installed within active woodpecker cavity-tree clusters. Our comparison was restricted to cavity-tree clusters in longleaf pine (Pinus palustris) and loblolly (P. taeda)-shortleaf (P. echinata) pine habitats where woodpecker groups were present for the entire period between 1983 and 1999. Excavation rate of new cavities was significantly higher in longleaf pine habitat when artificial cavities were not available than during the subsequent period when artificial cavities were provided in all active cavity-tree clusters. In loblolly-shortleaf pine hahirat, we did not detect a significant difference in the rate of new cavity excavation between the periods before and after the use of artificial cavities. We attribute the difference in results between habitats to a relative scarcity of cavities in loblolly-shortleaf pine sites due to a higher hark beetle-induced cavity tree mortality.