The Black-capped Chickadee is essentially non-migratory, with seasonal movements occurring irregularly. These sporadic movements are generally considered irruptions rather than true migrations. Black-capped Chickadees have a wide distribution, ranging from Alaska and southern Canada south to northern Arizona and east to the mid-Atlantic coast [Smith 1993 (BNA)]. During the breeding season, chickadees predominantly glean insects for food, while in the winter they feed about 50% on insects and 50% on seeds and berries [Smith 1991]. They can be found in deciduous or mixed deciduous/coniferous woodlands, often preferring the woodland edge [Smith 1993 (BNA)]. However, during winter irruptions, chickadees may occasionally be found in atypical habitats such as in large cities [Bent 1946, Smith 1993].
Irruptions occur irregularly and are thought to be influenced by fluctuations in northern seed crop production [Bock and Lepthien 1976]. During years when irruptions occur, fall movements can be quite extensive [Veit and Petersen 1993]. In addition to the large numbers of chickadees that may move through an area, the movements are all the more obvious because they occur during the day. These mass movements are composed almost entirely of immature birds and tend south to southwest [Smith 1993 (BNA)]. While the breeding range overlaps the wintering range, Black-capped Chickadees can be found both north and south of their normal range during irruption years [Smith 1993 (BNA)]. Spring movements are considerably less pronounced [Bent 1946, Veit and Petersen 1993], and the direction of movement may not be obvious. However, spring movements generally tend northeast [Brooks 1987].
Wintering chickadees typically congregate in small, loose flocks [Bent 1946]. Flock composition appears to be stable [Bent 1946], with an established hierarchy present [Smith 1993 (BNA)]. Winter populations vary considerably from year to year and it is believed that during irruptions, chickadees typically move farther south than Massachusetts [Veit and Petersen 1993]. This assumption is based on the fact that winter population fluctuations do not necessarily correlate with irruption movements in the previous fall in Massachusetts [Veit and Petersen 1993].
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Observations
Black-capped Chickadees do not migrate, i.e. do not undertake regular seasonal movements every year. However, they disperse and/or irrupt in response to fall and winter food supplies, mostly natural tree seed crops. High concentrations were observed in VT and MA A sites, with remarkably few in CT A sites, except for a single passing flock in period 1 in 1966. The Deerfield R. B sites in MA also had remarkably few chickadees. They were commonly recorded in all other sites in all states.
The dispersal of winter flocks results in lower concentrations of this species in all states as the season progresses. It should be noted that with early nesters such as the Black-capped Chickadee, adults who are incubating eggs might avoid detection in later censuses. This species was by far the most abundant bird recorded in the three-year study. |
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