One of 4 birds that John James Audubon “discovered” and named while in coastal South Carolina, the Carolina Chickadee is a southeastern member of the family Paridae, although it ranges northward to New Jersey and Pennsylvania and westward to Kansas and eastern Texas (Figure 1). This is an active, acrobatic bird that often gleans insects, larvae, or small spiders from the tips of branches. As a winter resident, this small bird must contend with cold temperatures and potential heat loss; through a variety of behavioral, physiological, and anatomical adaptations, 40 to 60% survive the winter. Like Black-capped Chickadees (Poecile atricapilla), wintering Carolina Chickadees form flocks that travel and forage together. The highest-ranking males and their mates that survive the winter breed within the flock's territory the following spring. Lower-ranking individuals are usually forced off the winter flock's territory, although a few males remain on the territory as summer “floaters.” The Carolina Chickadee typically produces only 1 brood a year. Throughout the annual social cycle of this species, members of the group (whether a mated pair, a family, or a flock) constantly communicate vocally and visually with each other and with rivals.
Carolina and Black-capped chickadees are similar in appearance; not surprisingly, the 2 are often confused. Although morphologically similar, they are genetically distinct species, with details of their phylogenetic relationship to each other and to other members of the genus Poecile not yet fully resolved. Careful observation allows for numerous ways to distinguish between Carolina and Black-capped chickadees. For example, the Carolina Chickadee has noticeably less white in its greater wing coverts than does the Black-capped, and it has a proportionately shorter tail. The Carolina Chickadee's 4–6 note song, and its broader song repertoire, contrast with the Black-capped's simple fee-bee song.
Although most Carolina Chickadees live south of their Black-capped relatives, the 2 species overlap and often hybridize where their ranges meet. Analysis of the structure and dynamics of these hybrid zones is the focus of ongoing studies in Virginia ( Sattler and Braun 2000 ), Ohio (T. C. Grubb, Jr., and C. L. Bronson unpubl.), and Pennsylvania ( Cornell 2001 , Mullen 2001 , RLC).
Other aspects of the Carolina Chickadee's natural history that have received considerable attention include: effects of environmental conditions on metabolism and behavior (for example, Grubb Grubb 1977b , Grubb 1978 ; Pravosudov et al. 1999a ; Doherty et al. 2001 ); dynamics of social relationships and complexity of flock-dominance structure ( Mostrom 1993 ); major patterns of breeding biology and demography, including long-term work in Tennessee (T. D. Pitts unpubl.); and northward range expansion of the species (P. Hess unpubl.).
Yet despite the broad geographic distribution of this species and its willingness to use artificial nests sites, facilitating demographic study, extensive gaps in its natural history remain. Countless opportunities await those who wish to contribute to our understanding of this common and intriguing bird.