Availability and abundance of prey for the red-cockaded woodpecker
Over a 10-year period we investigated red-cockaded woodpecker (Picoides borealis) prey use, sources of prey, prey distribution within trees and stands, and how forest management decisions affect prey abundance in South Carolina, Alabama, Georgia, and Florida. Cameras were operated at 31 nest cavities to record nest visits with prey in 4 locations that ranged in foraging habitat from pine stands established in old fields to an old-growth stand in south Georgia. Examination of nearly 12,000 photographs recorded over 5 years revealed that, although red-cockaded woodpeckers used over 40 arthropods for food, the majority of the nestling diet is comprised of a relatively small number of common arthropods. Wood cockroaches (Blattaria: Blattellidae) were always the most common prey fed to nestlings, comprising 54.7% of their diet. Other common prey included caterpillars (Lepidoptera larvae), spiders (Araneae), woodborer larvae (Coleoptera: Cerambycidae), centipedes (Scolopendromorpha), and ants (Hymenoptera: Formicidae). Woodpeckers selected prey based on their abundance on tree boles and we saw no evidence that they preferentially selected cockroaches or other types of prey. Analysis of the woodpecker's diet and the community of arthropods on tree boles suggests that the food web supporting red-cockaded woodpeckers is detritus-based. However, the woodpeckers use a variety of arthropods and readily adapt to locally or temporally abundant food sources. Red-cockaded woodpeckers feed primarily on crawling arthropods that move onto the bole from the soil/litter layer. Therefore, most prey are not exclusively bark residents. Prey distribution within and between trees was regulated by bark thickness and, more importantly, bark flakiness. More prey were found near the base of the bole and in dead branches in the canopy where thick or loose, flaky bark provided better refuge. Arthropod abundance increased on trees up to 60-70 years of age after which it remained relatively constant on older trees. Prescribed burning had little effect on wood cockroaches but both winter and summer prescribed burns reduced ant and spider biom ss. We found no evidence that herbaceous understory cover or diversity increased arthropod abundance on tree boles. Longleaf pine (Pinus palustris) trees harbored over twice as much arthropod biomass during the day as similar size loblolly pines (P. taeda) in the same area. The digerence was due to the loose, flaky bark of longleaf pines. Longleaf pines 25-cm (10 in) diameter breast height (dbh) or larger harbored the most arthropod biomass. Our results suggest that management of foraging areas can be fairly flexible without harming the arthropods on which red-cockaded woodpeckers rely.