Researchers analyze precision of secretary bird's deadly kick

Researcher Steve Portugal, animal physiologist at Royal Holloway, University of London, describes secretary birds as "ninja eagles on stilts."
By Brooks Hays  |  Jan. 25, 2016 at 2:37 PM
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LONDON, Jan. 25 (UPI) -- The secretary bird, Sagittarius serpentarius, is a mostly terrestrial bird found among the grasslands of sub-Saharan Africa. For the first time, scientists have quantified the mechanics of the bird's deadly kick.

According to their findings, the kick enables an energy transfer the equivalent of five times the bird's mass -- all in a hundredth of a second. The kick is exceptionally precise. It has to be, the secretary makes lunch of some of the deadliest snakes on the planet.

A secretary bird named Madeleine living at the Hawk Conservancy Trust in Hampshire, England, is trained to strike rubber snakes like her relatives do in the wild. Researchers pulled a fake snake atop a force plate to record Madeleine's strike.

The plate revealed a surprising amount of power, considering the secretary bird's slight frame and awkward gait.

Madeleine's strike is delivered with 195 Newtons of force. On average, her foot was in contact with the rubber snake for only 15 milliseconds, or 0.015 seconds.

Researchers, who published their findings in the journal Current Biology, say it's difficult to compare the bird's kick with other animals, as similar striking techniques are rare in nature and not often studied.

According to The Atlantic, a barn owl strikes with a force 14 times its own body weight. But while the owl does it by dropping from the sky, the secretary bird generates its power from a standstill and at lightning speed -- and while balancing on one leg.

Dr. Steve Portugal, animal physiologist at Royal Holloway, University of London, describes secretary birds as "ninja eagles on stilts."

"They look amazingly dinosaur-like; they strut through open plains... looking down the whole time," Portugal told the BBC. "They wait for a snake to be flushed out ahead of them -- and then they suddenly run over and start to deliver the kick to the head."

And unlike other birds, which close their eyes during the last moment of their strike, the secretary bird keeps its eyes open throughout the kick.

"They use vision to estimate where the food is and then close their eyes at the last minute," Portugal told The Atlantic. "But a secretary bird keeps its eyes constantly open, and locked onto its prey. For a bird to rely so much on vision is quite strange. I wasn't expecting that."

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