Processes Regulating the Population Dynamics of Red-Cockaded Woodpecker Cavities

Abstract

Recent studies of the endangered, cooperatively breeding red-cockaded woodpecker (Picoides borealis) have shown that the number of woodpecker groups in a population is directly dependent on the number of clusters of suitable cavities. Effective management therefore depends on an understanding of the processes underlying the gain and loss of cavities from woodpecker cavity populations. We examined the dynamics of the cavity populations at 4 study sites in North Carolina, USA. All were found to be stable or expanding, but 3 were heavily supplemented by the construction of artificial cavities and the use of cavity restrictors. Cavity losses were due almost entirely to cavity enlargement by other species and to cavity tree mortality. Cavity gains through new excavation were not correlated with cavity losses, and some groups became deficient in cavities. The use of artificial cavities and of cavity restrictors by managers negatively influences natural excavation by red-cockaded woodpeckers, but over the short term, these tools will be necessary to mitigate cavity losses and supplement cavity gains. A long-term management strategy, however, must focus on more effective preservation of the old, living pine trees required by the woodpeckers for cavity excavation.