The Red-cockaded Woodpecker, one of nine species within the genus Picoides in North America, depends on old growth southern pine forests for food and habitat. As a result of this dependence, its populations have been vulnerable to elimination, fragmentation, or modification of those forests by man. Conversion of favored longleaf pine (Pinus palustris) forest to slash pine (P. elliottii) has also been linked to population declines in this woodpecker.
Once considered common in the South, the Red-cockaded Woodpecker has disappeared from much of its range and has been considered Endangered since 1968 ( U.S. Department of Interior 1968 ). This status, as well as its continued broad distribution (albeit of small and declining populations) in the southeastern United States and its occurrence on many federal lands, has made the Red-cockaded Woodpecker the subject of intensive study since the early 1970s. Indeed, it may well be the most studied woodpecker species in the world. Jackson's ( Jackson 1981a ) annotated bibliography of the species includes 1,790 entries, Marion and Hagedorn's ( Marion and Hagedorn 1991 ) review covers selected literature through 1990, and three symposia since 1971 have focused on this woodpecker ( Thompson 1971 , Wood 1983b , Kulhavy et al. in press).
Like most of its congeners, the Red-cockaded Woodpecker is rather sedentary and not known to migrate, although on occasion individuals may wander far, perhaps a result of habitat destruction. Unlike its North American congeners, this is a social species that lives in family groups, often called clans, with a cooperative breeding system. The cluster of cavity trees used by the family group and the group itself led early observers to refer to this species as "colonial" and to the cavity tree cluster as the "colony site." These misnomers have died hard and given casual observers a false sense of the species' abundance. Throughout this account the site of the cavity tree or trees occupied by a family group will be referred to as the "cavity tree cluster."
Unlike most woodpeckers, the Red-cockaded typically excavates nest and roost cavities in living trees (several pine species), cavities that may be used for decades. Above and below each cavity the birds also excavate tiny holes-resin wells-from which resin exudes, apparently protecting the birds and their nests from climbing rat snakes (Elaphe obsoleta, E. guttata). Their social system, unusual cavity sites, and resin wells are hallmarks of a species so different among woodpeckers that a unique vocabulary has become associated with it ( Jackson and Thompson 1971 ).