An Evaluation of Aerial Survey Techniques for Red-Cockaded Woodpeckers

Abstract

The efficiency of using a fixed-wing aircraft to locate red-cockaded woodpecker (Picoides borealis) colonies in pine (Pinus spp.) forests of the southeastern United States was tested during 1980-82 using inexperienced observers under clear skies in summer and under clear and overcast skies in winter. Later, under actual survey conditions with experienced observers, preliminary superficial coverage of the area from the ground followed by intensive coverage from the air resulted in location of 80% of the colonies that were later found by intensive ground survey. In both experimental and actual surveys, successful aerial location of colonies was based on: (1) high visibility of gum on the trunks of cavity trees above and below redcockaded woodpecker cavities; (2) species preference for excavating in pines located in relatively open stands; (3) species habit of typically excavating cavities below the lowest branch; and (4) usual presence of multiple cavity trees per colony. Flight altitude was approximately 150 m and flight speed 60 knots in both Cessna 150 and 172 aircraft. Highest accuracy can probably be attained by double coverage of the area using perpendicular transects on calm, overcast, winter days. Aerial surveys can be used to locate colonies of redcockaded woodpeckers on inaccessible areas or in situations where intensive ground survey is not feasible. J. WILDL. MANAGE. 49(4):1083-1088 The red-cockaded woodpecker is an endangered species that is endemic to the mature pine forest ecosystems of the southeastern United States. Because its home range often exceeds 80 ha, the species is limited to large tracts of forest and, consequently, is difficult to census. Estimates of red-cockaded woodpecker abundance can, however, be made by extrapolating from the number of active sites. Although the species is not truly colonial, the colony is occupied by a clan, usually consisting of a breeding pair and one or more nonbreeders (generally male offspring from previous seasons). Typically each bird in a clan has a roosting cavity in a living mature pine, and the cavities of each clan are clustered in nearby trees. Colony sites are traditional, being used by succeeding generations of birds and often include cavities that have been abandoned by red-cockaded woodpeckers or usurped by other species. Cavity trees take on a conspicuous appearance due to the excavation of resin wells, from which gum flows, around the cavity entrance, eventually coating the tree with a white glaze (Hooper et al. 1980). When a cavity has been abandoned, the gum dries, turning yellow-white at first, but eventually darkens as a result of bei g covered by soot from fires or by dust from he air. The conspicuousness of the cavity trees is increased because cavities generally are below the lowest branch and open to the south or west (Locke and Conner 1983). Furthermore, vegetation in an active is typically open-at least at cavity height (Hooper et al. 1980). Because of the extensive forested areas f the Southeast, locating sites by systemati ally searching suitable habitat from the groun is labor-intensive and costly. The objectiv s of the study were to evaluate: (1) the eff ctiveness of using fixed-wing aircraft to locate prev ously unknown colonies, and (2) the abilities of observers to locate known sites from the air at different times of year, under different weather conditions. The exp riment was funded by the U.S. For. Serv. Southeast. For. Exp. Stn., Clemson Univ., through Coop. Res. Agreement 18-750. Surveys we e funded under contracts to Eco-Inventory Stud., Inc., from the U.S. For. Serv., U.S. Army Corps of Eng., U.S. Bur. of Land Manage., and United Gas Pipeline. M. R. Lennartz provided encouragement and stimulating discussion throug out the study. B. J. Schardien Jackson assisted with the experimental study and surThis content downloaded from 207.46.13.131 on Sat, 15 Oct 2016 04:20:31 UTC All use subject to http://about.jstor.org/terms 1084 RED-COCKADED WOODPECKER AERIAL SURVEY * Jackson J. Wildl. Manage. 49(4):1985