When Chickadees Sound The Alarm


July 08, 2005

An untrained ear may hear only "chick-a-dee-dee-dee-dee-dee." To a tiny black-capped chickadee, though, the call could be loosely translated as: "Yikes! Get a load of that pygmy-owl! I'll need the whole flock to help drive it away!"

Citing an "unsuspected level of complexity and sophistication in avian alarm calls," researchers have concluded that the chickadee's familiar call varies with the size of a potential predator, influencing the number of recruits joining forces to mob it and send it packing.

Larger predators such as great horned owls and gyrfalcons are apparently deemed lesser threats to the petite songbirds because of their ungainliness, the study found. But more nimble predators such as saw-whet owls or northern pygmy-owls can lead sentinel chickadees to repeat the "dee" note or syllable of their calls -- essentially a plea for reinforcements from the flock.

"Certainly, what we're seeing is one of the most sophisticated alarm call systems that's been discovered," said Christopher Templeton, a graduate student at the University of Washington who completed the research for his master's degree thesis while at the University of Montana. Whether a similar call-to-arms exists among other species will require further study.

Chickadees have several calls at their disposal. Their high-frequency "seet" call warns of danger in the air, while the "chick-a-dee" call, depending on the context, can cue other birds about food, identity or predators that have perched too close for comfort.

In the face of danger, the vigilant songbirds already have proven adept at recruiting a host of like-minded species. In the wild, their warning call has brought everything from warblers and nuthatches to sparrows and small woodpeckers flying to the rescue -- about two dozen species in all, according to one past study.

The latest study, published in a recent issue of the journal Science, came from Templeton and his University of Montana co-authors, Erick Greene and Kate Davis.

When they played a recorded chickadee call originally made in response to a great horned owl, only part of a captive flock of six birds headed toward the speaker. But when the scientists played a longer call with more "dee" notes, made in response to a northern pygmy-owl, "basically the whole flock comes right to the speaker and gets really agitated." Dive-bombing or mass fluttering often persuades a predator to move on.

"Imagine if you were out in the woods and there was a swarm of 100 mosquitoes swarming in your face, and you could step 20 feet away and be rid of them," Templeton said. "So that's kind of the idea."

-- Newsday

Quick Takes

Toss the ball

Sometimes an idea is so silly that you instinctively know it doesn't make sense.

That's how it is with the latest fitness trend toward using exercise balls instead of office chairs at work. Fitness enthusiasts call it "active sitting." They argue that the struggle of staying on a ball while, say, studying a balance sheet strengthens core back and spine muscles.

Researchers at the University of Waterloo, Ontario, in a study sponsored partly by the American Council of Exercise, found this to be untrue: They concluded that there isn't much difference in the degree of muscle activation between sitting on a ball or chair.

In fact, Stuart McGill, a spinal biomechanics expert who worked on the study, warns that sitting on an exercise ball all day could result in uncomfortable soft-tissue compression.

Bottom line: You may have more fun rolling back and forth in front of your computer, but it won't give your muscles more exercise. This is one fitness fad you should skip.

-- Mary Beth Regan

Did you know...

The majority of insect stings in the United States come from wasps, yellow jackets, hornets and bees. The severity of a sting reaction varies from person to person. A normal reaction will result in pain, swelling and redness confined to the sting site. Simply disinfect the area (soap and water will do) and apply ice to reduce the swelling.

-- American College of Allergy, Asthma & Immunology


Women's libido, testosterone studied

PHILADELPHIA -- A new study has found that the quality of women's lives in the bedroom has nothing to do with the amount of testosterone in their blood.

This might seem to be bad news for the score of drug companies developing testosterone products in hopes of tapping the estimated $1 billion market for a female counterpart to Viagra.

"Our study is going to frustrate a lot of doctors," said the lead author, Susan Davis, an endocrinologist at Monash Medical School in Australia. Treating female sexual complaints "is not just about giving testosterone. It's far, far more complicated."

But the Australian researchers who conducted the study are not counting out testosterone. While levels in the blood may be meaningful, levels in the brain, bone and fat -- where the hormone can't be measured -- may affect the female libido.

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