Do Hummingbirds Sleep?
It never ceases to amaze me the shear fascination people have with hummingbirds.I am no different then anyone else in this regard. Since I have been researching and writing about hummingbirds, my friends have asked me some very interesting questions about hummingbirds. This blog post is the result of one such question. My friend wanted to know if hummingbirds sleep.
Yes, hummingbirds do sleep. They do so at night by entering into a state known as torpor, which is a state similar to hibernation. Hummingbirds must enter this state to ensure that the birds won’t actually starve to death before down. Torpor is a type of deep sleep where an animal lowers its hart and metabolic rate. In a state of torpor the hummingbird lowers its metabolic rate by as much as 95%. A torpid hummingbird consumes up to 50 times less energy than when awake. The lowered metabolic rate also causes a cooled body temperature. A hummingbird’s night time body temperature is maintained at a level which is barely sufficient to maintain life. This level is known as their set point and it is far below the normal daytime body temperature of 104 degrees F or 40 degrees C known for other birds of similar size.
There are many reasons why the hummingbird must enter into a state of torpor. Hummingbirds are among the smallest of all warm-blooded animals, and they also lack the insulating downy feathers that are typical for many other bird species. Due to their small body size and lack of insulation, hummingbirds rapidly lose body heat to their surroundings. Even sleeping hummingbirds have huge metabolic demands that must be met in order for them to simply survive the night when they cannot forage. By entering into a state of torpor, a hummingbird is able to save enough energy to survive cold nights by lowering their internal thermostat.
There are several types of torpor. The various types of torpor are classified mostly by duration and season. If the state of torpor takes place over a long period of time during the winter, it is known as hibernation. However, unlike hibernation, hummingbird torpor can occur on any night of the year so it is referred to as daily torpor or noctivation.
Hummingbirds are not the only birds known to enter into a state of torpor. Other birds that are known to enter into a state of torpor include swallows and swifts. Scientists think that most small birds living in cold regions, such as chickadees, rely on torpor to survive long cold nights. Rodents, bats and other small mammals typically show some form of regulated hypothermia during cold weather, and these animals can only rely upon daily torpor during the winter months when they are not breeding. For hummingbirds, noctivation is possible on any night of the year.
The ability of the hummingbird to sleep by entering into the state of torpor literally saves the birds life. The ability to enter into a state of torpor will literally prevent it from starving to death before dawn. Isn’t it amazing how nature provides each species of animal the ability to help insure its own survival?