Implications of home-range estimation in the management of red-cockaded woodpeckers in South Carolina

I undertook a behavioral study to determine red-cockaded woodpecker (Picoides borealis) home-range size at the Savannah River Site, South Carolina, USA. In this location, because much of the timber was harvested in the late 1940s and early 1950s, the available habitat largely consisted of younger trees (e.g., less than 45 years old), not generally considered prime habitat for this species. From 1992 to 1995, I observed seven groups of red-cockaded woodpeckers to determine year-round home-range size. Most of the previous home-range studies on this species used the minimum convex polygon approach to estimate the size of the home range. I compared the minimum convex polygon and fixed kernel home-range estimation methods for each group. I found that the fixed kernel method gave consistently smaller estimates of home range than did the minimum convex polygon, a result directly related to the methodologies of the techniques. Mean home-range sizes for the 95% level were 56.9 ± 5.2 S.E. ha with the fixed kernel versus 91.9 ± 11.7 S.E. ha with the minimum convex polygon. Core area (50%) means were 4.5 ± 0.5 S.E. ha for the fixed kernel versus 16.7 ± 2.4 S.E. ha with the minimum convex polygon. It is recommended that future home-range studies use the fixed kernel estimator rather than the minimum convex polygon as it gives a more realistic and appropriate depiction of the area actually used by the birds within a given group. In estimating the number of groups that may be accommodated in a particular area, the mean home-range size as well as its shape need to be considered. Home-range size estimates at the Savannah River Site were similar to those obtained elsewhere in the species’ range. Red-cockaded woodpeckers, in spite of the prevalence of relatively young forest structure, did not increase their home-range size to compensate for the paucity of older, more mature pine habitat.