Red-Cockaded Woodpecker Nest-Cavity Selection: Relationships with Cavity Age and Resin Production

Abstract

We 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. We 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 h 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-h 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.

Tree cavity occupancy by nesting vertebrates across cavity age

“…Except for northern flickers and red‐breasted nuthatches, excavators in our system typically excavate a fresh cavity for nesting each year, and these cavities became available for secondary users in subsequent years. At the community‐level, our result that occupancy was highest in cavities age 1 year post‐excavation is similar to the results of shorter‐term and single‐species studies (Conner et al , Aitken et al , Mazgajski , Gentry and Vierling ). These findings support hypotheses predicting that fresh cavities offer an advantage to secondary cavity users in terms of lower predation risk, better microclimate regulation, or fewer ectoparasites, compared to older cavities (Nilsson , Sonerud , Wesołowski , Tozer et al ).…”

Mitochondrial Perspective on the Phylogenetic Relationships of the Parula Wood-Warblers

“…Active cavity tree clusters were visited several times per year. The age of many cavities within particular trees was determined by the year (and month if possible) they were completed, not the year that excavation began (see Conner et al 1998). During each visit, we determined occurrence and causes of cavity tree mortality, such as wind throw, wind snap, fire, bark beetles, and lightning (see Conner et al 1991).…”

“…Longleaf pines are known to produce larger amounts of resin than loblolly and shortleaf pines (Hodges et al 1977), and are able to maintain a higher yield of resin when stressed by woodpecker excavation at resin wells than loblolly and shortleaf pines (Conner et al 1998; Fig. 1).…”

Resin-Barrier Maintenance as a Mechanism of Differential Predation Among Occupants of Red-Cockaded Woodpecker Cavities

“…The figure illustrates the potential for a positive indirect effect of rat snakes on Red-cockaded Woodpeekers, through pathway P^^Pp^. perhaps the incidence of helpers (Hodges et al 1979, Neal et al 1993, Ross et al 1997, Conner et al 1998, 2001, Kappes 2004). …”

“…Sets of cavity trees, termed clusters (Walters 1990), are typically aggregated within a group's territory. The most recently completed cavity often becomes the breeding male's roost (Conner et al 1998) and the group's nest cavity (Ligon 1970). Breeding females, helpers, and juveniles roost individually in older cavities, including former nest holes.…”