Comparison of arthropod prey of red-cockaded woodpeckers on the boles of long-leaf and loblolly pines
Red-cockaded woodpeckers (Picoides borealis) forage on the boles of most southern pines. Woodpeckers may select trees based on arthropod availability, yet no published studies have evaluated differences in arthropod abundance on different species of pines. We used knockdown insecticides to sample arthropods on longleaf (Pinus palustris) and loblolly pine (P. taeda) to determine which harbored the greater abundance of potential prey. Longleaf pine had significantly greater arthropod abundance (278±44.4/tree, P=0.013) and biomass (945±28 mg/tree, P=O.O07) than loblolly pine (132±13.2/tree and 395±28 mg/tree). Certain groups were found in significantly higher numbers on longleaf, including Thysanura (P=0.0004), Hemiptera (P=0.0209), and Pseudoscorpiones (P=0.0277). Biomass of woodroaches (Blattaria: Blattellidae) also was greater on longleaf boles, but number of individuals did not differ significantly, suggesting that larger arthropods may prefer the bark structure of longleaf pine. We altered the bark surface of longleaf pine to determine whether bark structure may affect arthropods residing on a tree's bole. When the loose bark was removed by scraping, we recovered fewer arthropods from scraped than from unscraped control trees 8 weeks after scraping. We also lightly scraped the outer bark of both tree species and found that longleaf pine had significantly more loose, flaking bark scales than loblolly (P=O.0012). These results suggest that bark structure and not the chemical nature of the bark is responsible for differences in arthropod abundance and biomass observed on the 2 tree species. Retaining or restoring longleaf pine in red-cockaded woodpecker habitats should increase arthropod availability for this endangered bird and other bark-foraging species.