Head-turn­ing vi­o­lence helps tiny song­birds kill big prey

Muscat Daily - - WORLD -

Paris, France - They may be small and strik­ing, but shrikes are song­birds known for viciously im­pal­ing their vic­tims with a ra­zor-sharp bill al­though ex­perts have long won­dered about their abil­ity to sub­due much larger prey.

Now re­searchers say th­ese car­niv­o­rous killers use pow­er­ful beak-and-jaw mo­tions to shake their vic­tims vig­or­ously, whirling them around at speeds which cause in­juries akin to whiplash.

“We al­ready knew that they can kill sur­pris­ingly large an­i­mals for their size, but we didn’t know specif­i­cally how they do it,” said Dr Diego Sus­taita, lead au­thor of a study pub­lished in Bi­ol­ogy Let­ters jour­nal.

Al­though shrikes have sharply hooked, fal­con-like beaks which they jab into the head or neck of their prey, caus­ing par­tial paral­y­sis, they don’t have the large talons pos­sessed by other birds of prey to help them fin­ish the job.

But re­searchers at San Diego Zoo In­sti­tute for Con­ser­va­tion Re­search on Cal­i­for­nia’s San Cle­mente is­land found clear ev­i­dence of vi­o­lent shak­ing in a mo­tion which uses the vic­tim’s weight against it, Sus­taita said.

“The way that shrikes shake their prey is likely to be im­por­tant for im­mo­bil­is­ing and killing it be­cause the ac­cel­er­a­tions of the prey’s own body around its neck re­sults in forces that could break or dam­age the neck,” he said.

“The rate at which the shrikes shake their heads was sur­pris­ing, es­pe­cially with rel­a­tively large an­i­mals in their jaws!” he said, with the study sug­gest­ing the move­ment re­sulted in ac­cel­er­a­tions equiv­a­lent of around 6g-force.

For the study, re­searchers stud­ied footage of at­tacks by 37 log­ger­head shrikes in­volv­ing live do­mes­tic black mice and other crea­tures. In 28 cases, they ob­served prey-shak­ing be­hav­iour with the re­sults giv­ing a clear in­di­ca­tor of how the birds sub­dued larger crea­tures.

“They help ex­plain how a small song­bird is able to kill rel­a­tively large an­i­mals in ways that dif­fer from large rap­tors like hawks. Shrikes have some of the ‘equip­ment’ like the sharply-hooked beak, but not all, like the talons, and so they seem to have found an­other way to get the job done.”

Shrikes, he said, are dis­pro­por­tion­ately strong for their size but their abil­ity to kill is ac­tu­ally more re­liant on speed.

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