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Saturday, July 11, 2009

Hummingbird Pulls Top Gun Stunts

For its size, courting flier dives faster than a returning space shuttle

Source: http://www.sciencenews.org/ by SusankMiliushummingbird

During breeding season, the male Anna’s hummingbirds soar some 30 meters and then dive, whizzing by a female so fast that their tail feathers chirp in the wind. As the birds pull out of their plunge to avoid crashing, they experience forces more than nine times the force of gravity. “They look like a little magenta fireball dropping out of the sky,” says Chris Clark of the University of California, Berkeley.

Clark took advantage of the males’ predictable dive orientation, setting out a caged female, or even a stuffed female on a stick, to inspire birds to dive right in front of his video cameras. Males flew up and plunged over the female typically 10 or 15 times in a row, but one enthusiastic stunt flier completed 75 consecutive dives with a break of only a few minutes.

Analyzing the recordings revealed that birds at first flapped their wings as they dove. For a short period at their peak speed, the birds folded their wings and drilled down through the air at speeds up to 61 miles per hour.

Adjust for body length, and the world just got a new fastest bird, Clark says. The hummingbirds’ speed reached 385 body lengths per second, easily beating the peregrine falcon’s recorded dives at 200 body lengths per second. A fighter jet with its afterburners on reaches 150 body lengths per second, and a space shuttle screaming down through the atmosphere hits 207 body lengths per second. Then diving males stretch out their wings to pull out of their dive before crashing. If birds didn't have great strength for this maneuver, "their wings would just break off," Clark says.

Such prowess impressed Clark, but when he saw wild female birds watching the show … well. “Sometimes they looked bored or flew away,” he says. Males typically just kept on diving.

Hummingbird Diving In Action from Science News on Vimeo.

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