Cavity construction by reintroduced populations of Red-cockaded Woodpeckers (Dryobates borealis)

摘要

Although species reintroduction attempts are now common, monitoring of reintroduction attempts rarely extends beyond initial population establishment. This short timespan likely fails to document long-term population stability, subtle changes in behavior, and the potentially larger effects that some reintroduced species may have on other species. The Red-cockaded Woodpecker (RCW; Dryobates borealis) is an important habitat specialist and ecosystem engineer that excavates cavities in living trees. Excavation of natural RCW cavities can take years to complete, but they also persist for many years and are used by many other species. We quantified characteristics of cavity trees excavated by RCWs (n = 44) in two populations that were reintroduced to unoccupied areas more than 10 years earlier. We measured features associated with heartwood rot and used generalized linear mixed effects regression to determine whether these features differed for trees selected for cavity excavation compared with random neighboring trees. We also assessed population trends for cavity-nesting species that commonly used RCW cavities on one of the sites. Height of first live limb was the only factor distinguishing natural RCW cavity trees from control trees. Four of six cavity-nesting species monitored increased significantly following RCW establishment. The increases may relate to the many natural and artificial cavities created during the reintroduction effort. Future reintroductions of the RCW should lead to successful natural cavity excavation if sufficiently large trees with smaller live crowns are present. Future efforts may also benefit the broader community of cavity-nesting birds.