Secretary Birds Have a Killer Kick, New Study Shows

Snake-hunting Secretary Birds kill their prey by stomping on them while exerting a force equivalent to five times their own body weight, according to a new study.  What's remarkable about the bird's powerful kick is that the contact time between the bird's lanky legs and the snake is a mere 15 milliseconds.

"The exceptionally rapid strike contact duration is 1/10th of the time it takes to blink an eye, which takes around 150 milliseconds," Dr. Steve Portugal from the School of Biological Sciences at Royal Holloway, University of London, said in a news release.

Joined by Portugal was a team of researchers from the Royal Veterinary College and the Hawk Conservancy Trust. Their study focuses on a captive male Secretary Bird called Madeleine, which lives at the Hawk Conservancy Trust in Hampshire.

Secretary Birds are native to Africa and Asia, where they hunt venomous snakes using their rather long legs. Since a missed kill could have deadly consequences, the birds have learned to deliver accurate strikes that are powerful enough to stun and kill their prey in only one swift kick.

"Such rapid time, coupled with the exceptionally long legs, means the birds can't be using proprioception - the sixth sense we use to sense our position and movement," Dr. Portugal added. "Therefore, they are using visual targeting and feed-forward motor control - pre-planned movements - during strike events. This means the birds can only correct for a missed strike in the next kick -- once they've started a kick, they can't adapt it, and they have to wait for the next strike." (Scroll to read more...)

In the latest study, Madeleine was trained to attack a rubber snake to demonstrate the hunting techniques of this type of bird. Researchers measured Madeleine's kicks by putting a force plate - hidden under artificial grass - in the bird's enclosure and pulling the rubber snake across the force plate. 

"There are interesting potential technological applications in 'biologically inspired' control of exceptionally fast movement in robots and prosthetics," Dr. Monica Daley, a Senior Lecturer at the Royal Veterinary College, explained in a statement.  "A comparable task might be playing baseball with a prosthetic arm, which requires very fast, forceful and accurate arm movements for pitching and batting."

Their findings were recently published in the journal Current Biology. 

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