Hummingbirds do not drink at night. These tiny birds possess one of the highest metabolic rates among all animals, requiring constant energy intake. Their rapid metabolism means they are only a few hours from starvation without food. They employ specific strategies to manage energy needs, especially at night when foraging is not possible.
Daytime Fueling Strategy
Hummingbirds maintain their high metabolic rate by consuming large amounts of nectar and tiny insects throughout the day. They can eat one and a half to three times their body weight in food daily, visiting numerous flowers to meet energy demands. This intense feeding allows them to build up energy reserves, primarily glycogen and fat. These stored reserves provide the fuel to sustain them through the night, eliminating the need for nocturnal drinking or feeding.
Torpor: Nighttime Survival Mode
To survive periods without food, such as during the night or cold weather, hummingbirds enter a state called torpor. This condition is a controlled reduction in physiological activity, akin to a mini-hibernation. During torpor, their heart rate can slow from 500-1,200 beats per minute to fewer than 50 beats per minute. Their breathing also slows, and body temperature can drop by as much as 50 degrees Fahrenheit, sometimes approaching ambient temperatures. This reduction in metabolic activity allows hummingbirds to conserve energy, consuming up to 50 times less energy than when active.
Hummingbirds can regulate the depth of their torpor, utilizing shallow and deep states depending on environmental conditions and energy reserves. This physiological adaptation is a survival mechanism, enabling them to endure cold nights without expending calories or water to maintain their normal high body temperature. Torpor is distinct from sleep; while in torpor, their functions are shut down, and they do not receive restorative benefits of sleep.
Waking Up and Rehydrating
As dawn approaches, a hummingbird begins emerging from torpor. This awakening is a gradual process that can take 20 minutes to an hour, depending on torpor depth and surrounding temperature. To generate heat and raise body temperature, hummingbirds shiver, rapidly contracting their muscles. This process requires expenditure of remaining energy reserves.
Upon full arousal, the hummingbird is in immediate need of energy and rehydration. Their first priority is to quickly locate a food source, such as nectar, to replenish depleted energy stores. This rapid return to active feeding and drinking highlights the hunger and thirst experienced after a night spent in energy conservation.