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Hummingbirds Go Into A Winter Torpor
To Survive The Cold - 03/20/09

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Dear Bird Folks,

Where I live we usually see hummingbirds by late February. What happens to these little birds when we get a late spring snowstorm? They can't fly back to Mexico. Do they simply die or are they somehow able to hunker down and survive the cold?

- Steve, Puyallup, WA

I'm jealous, Steve,

You Westerners have over a dozen different species of hummingbirds, while we only have one here in the East. And now you tell me that your hummers return in February. Oh, man. We have to wait until the end of April, or even early May until our one species of hummingbird drags its ruby throat back for the summer. I am so jealous. Do you know how many more feeders I could sell if we had all those additional birds and a longer season? With a little extra business I could finally afford to quit my other job as Brad Pitt's body double. I'm tired of doing that. The Hollywood scene is starting to wear on me.

Hummingbirds, the world's smallest birds, have all sorts of adaptations to help them survive in a world of avian giants. They have super-long beaks to allow them to gather food deep inside flowers that other birds can't reach. And if their super-long beaks can't get the job done they have super-duper long tongues to collect food that's even harder to reach. (Actually, I don't know how long a "duper" is, but I've heard it's very long.) Hummingbirds can hover in mid-air, and if necessary, they can even fly backwards. They have been very successful at adapting to their environment. In fact, there are more species of hummingbirds in the Americas than the world's total number of eagle, falcon and hawk species combined.

Even with all their abilities, North American hummingbirds aren't real big fans of cold weather. They don't have the same downy insulation that many of other birds have. They don't have the ability to stash extra food for later like some birds do. And because their bodies are so small, they can't go for long periods without a good meal. Still, hummingbirds have evolved a way to make it through the night when the weather turns against them. Instead of trying to fight the cold, they simply give in to it and go into a short period of hibernation each night called "torpor." Torpor is often referred to as "temporary hibernation," which doesn't make much sense to me. Shouldn't all hibernation be temporary? If you're in permanent hibernation, you have a problem.

When a night is exceptionally cold a hummingbird will find a nice cozy branch to curl up on and shut its systems down. Slowly the bird's body temperature drops from around 100 degrees to nearly 50 degrees. Its breathing is almost nonexistent, going as long five minutes between breaths. When a hummingbird is in this state it has little knowledge of the outside world. You could easily walk up to this bird, stare at it, make faces at it, talk about it, or even stroke its little head and it will not respond. Sounds like a date I had once.

Though the bird appears to be fast asleep or even dead, it is, in fact, neither. While going into a state of torpor may seem like a great way to get a good night's sleep, the opposite is true. The bird's systems are so shutdown that its body can't reap the benefits of sleep. The little hummer needs to come out of the torpor about an hour or two before sunrise, at which time, it is thought, the bird becomes alive enough to go to sleep. The old Three Stooges line, "Wake up and go to sleep," actually makes sense to a hummingbird.

In North America the cold weather champ is the feisty little Anna's Hummingbird. While other hummingbirds move to the tropics to avoid our scary winters, the Anna's does very little migrating. It can be found as far north as Canada anytime of year. And since it doesn't spend all of its time making those annual ridiculously long distance flights the Anna's is the first hummingbird to breed each year. Starting as early as December this bird is pretty much finished with its domestic chores by May, when all of the other hummers are just coming back.

For the most part Anna's are West Coast birds. Until recently their realm was limited to the coastline of California, but in the past century they have been expanding their range eastward to New Mexico and north to Alaska. That's right, even Alaska has hummingbirds. While I'm sure our delicious feeders have helped these birds push into new territories, the real reason they are thriving has to do with our love of flowering plants and shrubs. Areas that once featured tumbleweeds now have well-watered posies.

Since you are seeing hummingbirds in February, Steve, I'm pretty sure those birds are hearty Anna's Hummingbirds. Even though a surprise cold snap or snowstorm can be tough on them, more often than not they make it through just fine. Maybe someday they'll expand their range into my part of the world and I'll sell enough extra feeders so I can stop being Brad Pitt. It needs to happen soon, though. I can only hold Angelina off for so long.



Artwork by Catherine Clark


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