Red-cockaded woodpecker nest-cavity selection: relationships with cavity age and resin production
The authors evaluated selection of nest sites by male red-cockaded woodpeckers (Picoides borealis) in Texas relative to the age of the cavity when only cavities excavated by the woodpeckers were available and when both naturally excavated cavities and artificial cavities were available. They also evaluated nest-cavity selection relative to the ability of naturally excavated cavity trees to produce resin, which is used by the woodpeckers to maintain a barrier against predation by rat snakes (Elaphe spp.). Longleaf pines (Pinus palustris) selected by breeding males as nest trees produced significantly greater resin yields at 2, 8, and 24 hours post-wounding than cavity trees used for roosting by other group members. This preference was observed in loblolly pine (P. taeda) and shortleaf pine (P. echinata) cavity trees only at the 2 hour resin-sampling period. When only naturally excavated cavities were available, red-cockaded woodpeckers in both longleaf pine and loblolly-shortleaf pine habitat selected the newest cavities available for their nest sites, possibly as a means to reduce parasite loads. When both naturally excavated and artificial cavity inserts were available, red-cockaded woodpeckers continued to select the newest cavity for nesting in loblolly-shortleaf pine habitat but not in longleaf pine habitat. Resin production in existing longleaf pine nest trees remained sufficient for continued use, whereas resin production in loblolly pine and shortleaf pine nest trees decreased through time, probably because of woodpecker activity at resin wells. For these latter tree species, breeding males switched to newer cavities and/or cavity trees with higher resin yields.