One of the most familiar and widespread birds in North America, the Black-capped Chickadee is a non-migratory species found coast to coast, including much of Canada and the northern two thirds of the United States. Resident throughout its range, this species has northern populations that must withstand short days and very cold temperatures during winter. Under such conditions, individuals lower their body temperature at night and enter regulated hypothermia, saving significant amounts of energy. In addition, they store food and have exceptional spatial memory to relocate cached items.
Despite its vast range, this species is remarkably homogeneous in its genetic make-up. Genetically, its closest relative is the Mountain Chickadee (Poecile gambeli). In its plumage, it looks more similar to the Carolina Chickadee (P. carolinensis), which hybridizes with the Black-capped throughout a narrow contact zone in the eastern half of the United States.
Chickadees are seen most readily during winter when non-breeding flocks visit backyard birdfeeders, flocks generally comprised of 3 to 12 individuals. Social interactions within these groups are structured by stable linear dominance hierarchies. The dominance status of birds in winter flocks is partly age-related, and has important fitness consequences when birds break out of flocks to breed as socially monogamous pairs in spring. High-ranking males are preferred by females both as social breeding partners and extra-pair copulation partners.
Black-capped Chickadees are remarkably well studied, with numerous populations that have been monitored over extended periods in North America. Wild individually marked populations have been studied for more than a decade by Smith in Massachusetts (annual monitoring from 1979 to 1990), by Ratcliffe and Mennill and their students in Ontario (since 1987), by Otter and students in British Colombia (since 1987), and Curry and students in Pennsylvania at the Black-capped/Carolina hybrid zone (since 1997), as well as many additional multi-year studies. Chickadees are also readily maintained in an aviary setting. Detailed studies by Sherry and students on neurobiology and behavior, and by Weisman and Sturdy and students on vocalizations and cognition have contributed to the understanding of this species. Readers wishing details on all aspects of the biology and ecology of Black-capped Chickadees should consult both Smith (1991), a monograph on the species, and Otter (2007), an edited volume on chickadees and titmice that focuses heavily on this species.