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A Wilder View: Hummingbirds and hibernation

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hummingbird
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Posted at 11:25 AM, Oct 17, 2021
and last updated 2021-10-17 13:25:18-04

MISSOULA — We all know that bears need to hibernate during the winter to save energy but hummingbirds need to save a substantial amount of energy on a daily basis going into a sleep as deep as death.

Back in 1832, Alexander Wilson first described a hummingbird in the sleepy state known as torpor in his book, American Ornithology; saying, “no motion of the lungs could be perceived…and, when touched by the finger, it gave no signs of life or motion.”

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Hummingbirds have enormous requirements of energy which leads them to have quite an appetite. So big in fact that it’s equivalent to the average human consuming an entire refrigerator full of food. The birds eat roughly three times their own body weight in nectar and insects per day.

But at night they can’t be out looking for food so they have to go into a deep sleep called torpor to save energy. Torpor allows them to lower their energy requirements by as much as 95%, meaning they consume up to 50 times less energy when in this state than when they’re awake.

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Not only are the birds small, but they also lack the insulating down feathers that are typical for many other bird species. On top of this to save energy during this sleep they're body temperatures lower to near hypothermic levels.

This means they are usually near hypothermia on cooler nights. So not only does torpor cause a sleep as deep as death these hummingbirds can go through a near death experience every night.

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Some people report finding “dead” hummingbirds in their yards, in the morning. But these usually are just hummingbirds in their deep sleep called torpid.

Montana is home to the Caliope Hummingbird which is the smallest bird in the United States and is also the smallest long-distance migrant in the world; traveling around 5,000 miles each year.