Experimental Reintroduction of Red-Cockaded Woodpeckers

Abstract

The Red-cockaded Woodpecker (Picoides borealis) is an endangered species endemic to the pine forests of the southeastern United States (Jackson 1971). Deforestation and habitat alteration have severely affected Red-cockaded Woodpecker populations; current populations are isolated and most are declining (Jackson 1971, Lennartz et al. 1983, Conner and Rudolph 1989, Costa and Escano 1989). The species has been extirpated from significant areas of suitable or potentially suitable habitat. The cooperative-breeding social structure (Ligon 1970, Walters et al. 1988) and the dependence on the availability of adequate roost and nest cavities (Walters et al. 1992) strongly influence the biology of the species. A direct consequence of this social structure in remnant populations is the demographic collapse resulting from the failure of or extended lag time involved in the natural replacement of breeding individuals. This effect becomes increasingly severe as individual woodpecker groups become more isolated in the declining populations (Conner and Rudolph 1989). Potentially, the recently available techniques of artificial cavity construction (Copeyon 1990, Allen in press) and translocation of first-year adults (DeFazio et al. 1987) have provided managers with the ability to minimize this problem. A major void in management procedures is the current lack of a technique to artificially establish woodpecker groups and populations de novo. Previous efforts to relocate Red-cockaded Woodpecker breeding pairs met with limited success (Odom et al. 1982, Jackson et al. 1983). The recent improvements in cavity-construction techniques and experience in translocating individual birds convinced us that it was time to revisit the issue of the reintroduction of breeding pairs to vacant habitat. An inactive cluster of cavity trees on the Davy Crockett National Forest in eastern Texas was chosen for the attempt. The site had been inactive for about two years. The site contained two natural cavities. One had a metal restrictor to reduce the enlarged entrance (Carter et al. 1989), and the other was a single artificial cavity (insert type). Cavity competitors, flying squirrels (Glaucomys volans) and Red-bellied Woodpeckers (Melanerpes carolinus), were removed as necessary before and during the reintroduction. Resin wells were reopened using a wood chisel prior to introduction of the birds. The chosen site was approximately 3.5 km from the nearest woodpecker group, which consisted of a breeding pair and a helper male. All three birds were color banded, and the helper had joined the pair during the previous six months. The helper male was known to have visited the reintroduction site at least once prior to the reintroduction. Due to the familiarity of this helper male with the site, we elected to use him as the reintroduction male. The reintroduction female was a bird of unknown origin associating with a male/female pair on the Davy Crockett National Forest. Eight additional clans were located within 10 km of the reintroduction site. Standard translocation techniques (DeFazio et al. 1987) were employed. Briefly, the birds were netted from their roost cavities, transported in mesh cages, and placed in a natural cavity (male) and insert (female) on the night of 17 February 1991. The respective cavity trees were approximately 20 m apart. Wire mesh was tacked over the entrances to contain the birds until dawn. A nylon cord attached to the mesh allowed the birds to be released by a person stationed at the base of each cavity tree. The birds were released simultaneously at dawn on 18 February. The birds immediately established vocal and visual contact, and remained in the immediate area for approximately 30 min. During this period, vocalizations and following behavior were similar to that which we have come to associate with successful translocations of juvenile birds to an established mate. It started to rain at this time, and we left the site. The two birds returned to the site on the evening of 18 February and roosted in the immediate vicinity, but not in the cavities. The birds were next checked on the evening of 20 February. The female was still present and roosted in the open. The male had returned to his original group and was roosting in his original cavity. Rather than relocate the male a second time, or depend on his voluntary return, we decided to obtain a second male. During the night of 21 February, we translocated a juvenile male (fledged 28 May 1990) from his natal group on the Angelina National Forest, Texas. The male was released from the introduction cavity shortly after the female became active on the morning of 22 February. Due to the distance (150 m) between the roost site of the female (still roosting in the open) and the introduction cavity for the male,