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Hummingbird Metabolism:
Ruby-throated "Hungrybirds"

They may be the tiniest birds on the planet, but Ruby-throated hummingbirds are the biggest eaters. In fact, no animal has a faster metabolism—roughly 100 times that of an elephant. Hummingbirds burn food so fast they often eat 1-1/2 to 3 times their weight in nectar and insects per day. Perhaps Ruby-throated "hungrybirds" is a more descriptive name for them!

Maybe this explains why people rarely see hummers when they aren't eating. In order to gather enough nectar, hummingbirds must visit hundreds of flowers every day. And just one day of cold temperatures or bad luck finding flowers can mean death. Hummingbirds push the limits, and live their lives only a few hours from starvation.

Saved by Torpor
Sometimes there is a day, or several days, of cold temperatures, and sometimes a hummingbird has bad luck. What happens to hummingbirds then? These tiny birds have devised a fascinating way to conserve energy when they can't be eating—at night or when the weather is too cold or too rainy for feeding. They go into a sleep-like state known as torpor. During torpor, the tiny bird's body temperature can drop almost 50 degrees. The heart rate may slow from 500 beats per minute to fewer than 50, and breathing may briefly stop.

A hummingbird consumes as much as 50 times more energy when awake than when torpid. If you were to find a hummingbird in torpor, it would appear lifeless. If a predator were to find one, it would be lifeless indeed! While torpor has benefits, there are risks too. It can take as long as an hour for the bird to come back into an active state, so a torpid hummer cannot respond to emergencies.

How do hummingbirds come out of torpor? As their heart and breathing rates rise, they start vibrating their wings. The use of any body muscles produces heat; that's why you get warm while exercising. The heat generated by the vibrating wings warms the hummer's blood supply. The warmed blood circulates throughout the tiny bird's body, and soon the hummer's body temperature is back up to its normal toasty 102.2 degrees.

Do an experiment with clay to learn more about torpor here:


Try This! Math Journaling Question
It may be hard to imagine the challenges hummingbirds face every day in order to stay alive.

"If you burned energy at the same rate as a hummingbird, how much of your favorite food would you need to eat per day? Assuming you are awake 16 hours each day, how much food would you need to eat per hour?"

The following steps will help you figure out the answer:

1. Calculate the number of Calories per ounce a hummingbird needs in a day. (A Ruby-throated Hummingbird needs 10 Calories per day and weighs 1/10 of an ounce.)

2. Figure your own weight in ounces.

3. If you burned food at the same rate (Calories/ounce) as a hummingbird does, how many Calories would you need per day?

4. How many Calories are in one serving of your favorite food? How much of this food would you need to eat per day?

5. If you're awake 16 hours in a day, how much of your favorite food would you need to eat per hour?


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