A hummingbird can spend the day darting between flowers, then become almost motionless overnight. Its secret is torpor: a temporary, hibernation-like state that lowers its body temperature and slows its metabolism. By using far less energy while it cannot feed, the bird can make it through the night on the fuel it gathered during the day.
What happens during torpor?
An active hummingbird burns energy quickly, especially while hovering. At night, nectar is unavailable, but staying warm still costs energy. In torpor, the bird’s heart rate slows and its body temperature drops, reducing that cost. It may look unusually still, but this is a normal energy-saving response, particularly on cold nights or when food has been scarce.
Torpor is not quite the same as sleeping or spending a whole winter in hibernation. For hummingbirds, it is typically a short-term strategy lasting through the night. Researchers discussing how hummingbirds survive their high-energy lifestyle note that a torpid bird can use only a fraction of the energy it would use while sleeping normally.
Waking up takes energy, too
As the bird emerges from torpor, it must warm its body before returning to its usual activity. That makes the next opportunity to feed important. A broad-tailed hummingbird, for example, may enter torpor when nights are cold or it has not found enough food; Cornell’s species guide describes how lowering its heart rate and body temperature helps it conserve energy.
It is a striking contrast: the same tiny bird that can hover with remarkable control can also slow down dramatically to survive until morning. Curious about another hummingbird feat? Try this bird-flight trivia question.