The black-capped chickadee (Poecile atricapillus) is a small, nonmigratory, North American songbird that lives in deciduous and mixed forests. The chickadee is the state bird of Massachusetts, USA. Its familiar call of chick-a-dee-dee-dee gave this bird its name. The chickadee total body length is 12–15 cm (4.7–5.9 in), with a wingspan is 16–21 cm (6.3–8.3 in) and a body mass of 9–14 g (0.32–0.49 oz). Sexes look alike, but males are slightly larger and longer than females.
The chickadee has fascinating eating habits. Insects (especially caterpillars) form a large part of their diet in summer. Seeds and berries become more important in winter. Like many other species in the family Paridae, black-capped chickadees commonly cache their food, mostly seeds but sometimes insects also. Items are stored singly in various sites such as bark, dead leaves, clusters of conifer needles, or knotholes. The chickadee can remember the location of caches up to 28 days. Within the first 24 hours, the birds can even remember the relative quality of the stored items.
The chichadee is also well known for its uncommon capability to lower its body temperature. During cold winter nights, these birds can reduce their body temperature by as much as 10 to 12 °C (from their normal temperature of about 42 °C) to conserve energy.