Black-capped Chickadee
Poecile atricapillus
The black-capped chickadee has a black cap and "bib" with white cheeks. Its underparts are white with buff-coloured flanks. Its back is unstreaked and greenish grey, and the tail and wings are slate grey. It has a black beak and legs, and dark brown irises. Males and females are generally similar, although males have a larger bib. They can also be distinguished based on a combination of weight and tail length. Tarsus length does not significantly differentiate sexes. Males have a wing length of 63.5–67.5 mm (2.50–2.66 in), a tail length of 58–63 mm (2.3–2.5 in), a bill length of 8–9.5 mm (0. Voice: The vocalizations of the black-capped chickadee are highly complex, with 16 distinct types of vocalizations being used to convey an array of information. These vocalizations are likely an evolutionary adaptation to their habitat; they live and feed in dense vegetation, and even when the flock is close together, individual birds tend to be out of each other's visual range.
ID text from Wikipedia, CC BY-SA 4.0
Chestnut-backed Chickadee
Poecile rufescens
It is a small chickadee, 11.5–12.5 cm (4.5–4.9 in) long with a weight of 8.5–12.6 g (0.30–0.44 oz). The head is dark blackish-brown with white cheeks, the mantle is bright rufous-brown, the wing feathers are dark gray with paler fringes. The underparts are white to pale grayish-white, with rufous or pale gray flanks. It is often considered the most vibrant of all chickadees. Joseph Grinnell was one of the first to provide a significantly detailed description of this variation. Voice: Chestnut-backed chickadees can be identified by their “chick-a-dee” call, with “dee” repeated a few times. Adults and older nestlings can also be identified by their hissing noise, which mimics a snake while protecting their nests. They rarely use their “gargle” calls.
ID text from Wikipedia, CC BY-SA 4.0
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