Monday, August 3, 2009 - 2:30 PM

COS 16-4: The effects of exurbanization on the food and habitat of pileated woodpeckers

Marie E. Wilson, Jordan M. Casey, and David G. Haskell. University of the South

Background/Question/Methods Dryocopus pileatus (pileated woodpeckers) are the largest woodpeckers in the United States. They require large trees for roosting, nesting, and feeding and these trees must be dead or dying for ease of excavation and presence of the woodpeckers' main prey of ants and grubs. Because of these habitat requirements, pileated woodpeckers are used as an indicator species for mature forests. However, their status in exurban areas, or places of low-density development beyond the suburban fringe, is poorly known. Because exurbanization covers a large and growing portion of the eastern U.S.A., we examined how pileated woodpeckers and their habitat vary across a gradient of exurbanization. We tested the hypothesis that presence of pileated woodpeckers is positively correlated with forest structure and food availability, in exurban and forested areas. We conducted the study in Sewanee, Tennessee, U.S.A., establishing 30 randomly located sample points evenly divided between exurban and forested areas. At each point we assessed pileated woodpecker presence through visual and vocal surveys; forest structure through measures of downed wood, standing trees, and understory density; and food availability through presence of ants and grubs in soil cores and pitfall traps.

Results/Conclusions We found no difference between the presence of pileated woodpeckers, amount and rot class of dead wood, and ant and grub abundance between exurban and forested areas. Mean tree diameter was larger in exurban areas most likely because many small trees had been removed by human landscaping. These data suggest that some exurban areas may provide habitat for pileated woodpeckers. However, more studies are needed to examine the breeding success and survival rates of pileated woodpeckers in exurban and forested areas. Because the mature forest characteristics that pileated woodpeckers prefer can be found in exurban areas, it is possible that other species requiring these characteristics could also find usable habitat in exurban areas. This could apply most specifically to those secondary cavity-nesting species that use old pileated woodpecker nesting cavities. More studies should be conducted to further explore the effects of exurbanization on other species that are thought of as indicating mature forests.