According to the lead researcher, this bird is like a 'ninja eagle on stilts.' Jason Shallcross
Robin Andrews 27 Jan 2016, 12:14

The secretary bird is a fearsome, aggressive predator. Found on the open grasslands of sub-Saharan Africa, it kills its prey by striking it with its claw using incredible speed and precision. A new study published in the journal Current Biology has revealed that this killing strike transfers five times the bird’s own weight to its hapless prey in one-hundredth of a second.

This 1.4-meter-tall (4.6-foot) bird, with its long, quill-like feathers that emerge from its head crest, certainly has a striking appearance, and its behavior is no less memorable. Despite its rather large wingspan, it prefers to hunt its prey on foot on its stilt-like legs.

A team of researchers, led by Dr. Steven Portugal, an animal physiologist from Royal Holloway, University of London, wanted to find out just how incapacitating its killing strike was. Although its prey can consist of small mammals, insects, crustaceans, lizards and bird eggs, it has a penchant for hunting down snakes.

With this in mind, an average-sized, 24-year-old male secretary bird called Madeleine – named as such due to the misidentification of his gender at birth – was chosen as the subject of the study. As he’s trained to strike rubber snakes as part of public displays at the Hawk Conservancy Trust in the U.K., the researchers decided to place these “snakes” onto plates attached to pressure detectors. Using high-speed video, several of Madeleine’s strikes were filmed, and the average strike force behind 45 individual kicks was calculated.

 

 

Each strike averages around 195 newtons (43.8 pounds) of force, meaning that the “snake” experiences an impact many times in excess of the bird’s own weight. Remarkably, this force is transferred to the snake within roughly 15 milliseconds. For comparison, blinking your own eyes takes ten times longer.

The average human male weighs 84 kilograms (185 pounds). If this person wanted to exhibit the same kind of force the secretary bird is capable of, he would have to stomp on the same snake with about 4,120 Newtons (926 pounds) of force – which would cause him to break his own leg.

 

 

Although other birds are capable of striking with far more force – the barn owl attacks with a force equivalent to 14.5 times its own body weight, for example – they are not able to do this from a standing start. The secretary bird’s precise killing strike likely evolved out of the necessity to not make a single mistake: If you’re hoping to kill and eat a venomous snake, striking out and missing your target may result in you getting fatally bitten.

“This unusual hunting strategy is only shared by one other bird, the unrelated seriema of South America,” Portugal explained to IFLScience. “This hunting mechanism seems to only emerge in open grassland environments that contain highly venomous prey.”

Despite this simple experimental set up, there were some problems. On multiple occasions, Madeleine got distracted by the extension leads to the pressure plate, and attempted to destroy these snake-like objects instead. He wasn’t too keen on the minor changes to his environment either.

“We had to try and find ways not to interfere too much with his schedule,” Portugal added. “It was like dealing with a diva-ish Hollywood starlet at times.”

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