Hummingbirds have high metabolic energy requirements, needing to eat 2-3x their own body weight in flower nectar and tiny insects each day. Unable to forage at night, but needing to maintain those demanding energy requirements, hummingbirds conserve energy by going into torpor. This physiological adaptation is a daily version of seasonal hibernation, and is a deep sleep where the hummingbird is able to lower their metabolic rate and body temperature to the minimum amount needed to sustain life. Scientists suspect that hummingbirds utilize this sleepy adaptation when they are unable to store adequate metabolic reserve to get through the night, such as when they exert extra daily energy during breeding season or during mid-seasons where nectar production is low.
Sketch and fact contributed by Karli Chudeau
Calder, W. (1994). When Do Hummingbirds Use Torpor in Nature? Physiological Zoology, 67(5), 1051-1076.