Factors That Influence Translocation Success in the Red-cockaded Woodpecker

To restore a population that had declined to 4 individuals by late 1985, 54 Red-cockaded Woodpeckers (P&ides borealis) were translocated at the Savannah River Site in South Carolina between 1986 and 1995. Translocation success was evaluated by sex, age, and distance between the capture and release site. For moves involving females, the presence of a resident male and the status of the male (breeder, inexperienced, or helper) also was assessed. Of the factors I evaluated, only the distance of the move was statistically significant with increasing success associated with increasing distance. The presence of a resident male at the female’s release site led to no more success than releasing the female concurrently with a male; nor did the male’s status appear to play a significant role in female translocation success. Overall, 31 of 49 (excluding nestlings) translocated birds remained at or near the release site for at least 30 days, resulting in a success rate of 63.2%. Of the birds that were successfully translocated, 51.0% had reproduced by July 1996. Received 2 March 1998, accepted 15 Oct. 1998. Endemic to the open pine woodlands of the South, Red-cockaded Woodpeckers (Picoides borealis) are cooperative breeders whose groups usually consist of a breeding pair and often one or more helpers, usually male offspring (U.S. Fish and Wildlife Service 1985). A series of cavity trees occupied by such a group is referred to as a cluster. These cavities are used year round for night roosting and as nest sites during the breeding season (Steirly 1957). Since 1970 the species has been considered Federally endangered primarily because of widespread habitat loss, which has fragmented the original population into many subunits, some quite small and/or isolated (U.S. Fish and Wildlife Service 1985). One such small population occupies the Savannah River Site in South Carolina. By late 1985 the number of Red-cockaded Woodpeckers had dwindled to one breeding pair and two single males (DeFazio et al. 1987), and the Forest Service began intensive management to prevent extirpation on the site (Gaines et al. 1995). With the nearest known Red-cockaded Woodpecker population 32 km away, natural recruitment of and colonization by new individuals was considered unlikely. Because Red-cockaded Woodpeckers prefer older, live pine trees for constructing their cavities (Steirly 1957, Jackson et al. 1979, Conner and O’Halloran 1987, Rudolph and Conner 1991) and few trees of sufficient age ’ Southern Research Station-USDA Forest Service, Dept. of Forest Resources, Clemson Univ., Clemson, SC 29634-1003; E-mail: [email protected] and diameter were available, Forest Service personnel installed 305 artificial cavities (see Allen 1991 for details on artificial cavity construction and installation). Other management activities have included: (1) restricting cavity access by other larger woodpecker species with metal “restrictor” plates (Carter et al. 1989), (2) removing southern flying squirrels (Glaucomys volans) encountered while monitoring cavities and squirrel nest boxes, and (3) improving habitat quality by controlling the hardwood midstory vegetation that causes woodpeckers to abandon their cavities (Conner and Rudolph 1989, Costa and Escano 1989, Hooper et al. 1991, Loeb et al. 1992). In an effort to stabilize and eventually increase the population at the site, the Forest Service began a program of translocating woodpeckers from populations outside of and within the site. The objectives were to increase the number of breeding pairs, bolster the overall population size, and minimize potential adverse genetic consequences arising from small population size (Allen et al. 1993, Gaines et al. 1995). Here I assess the results of 10 years of Red-cockaded Woodpecker translocations at the Savannah River Site to determine the variables most likely to contribute to successful translocations, an important strategy in the recovery of small, isolated popula t ions . STUDY AREA AND METHODS Study area.-The Savannah River Site lies within the Upper Coastal Plain physiographic region in Aiken, Allendale, and Barnwell counties in South Caro-