Black-capped Chickadee
Poecile atricapillus

f5 @ 1/2500s, ISO:800, Nikon D3S w 500mm

"Black-capped Chickadee," Wikipedia, the free encyclopedia. On 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. Such a capacity for torpor is not very common in birds. Other bird species capable of torpor include the common swift Apus apus, the common poor-will Phalaenoptilus nuttallii, the lesser nighthawk Chordeiles acutipennis, and various species of hummingbirds.
Anchor Point, Alaska