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In 1978 , a group of researchers in a science laboratory at Queen ’s University in Canada clustered around a plexiglass box enclosing a treadmill … with a pigeon walking on it . The purpose behind this comical conniption was to judge and answer an age - old dubiousness : Why do pigeons curtsy their heads ?
Head - bobbing is as much a characteristic of pigeon ' personal identity as is their inclination to swarm us at the slightest suggestion that we might be harboring a snack . Bopping their head as they stalk about pecking the undercoat for crumbs , these birds seem to be furrow to some secret measure , as if they ’re all advert a dumb disco in the township lame .
Head-bobbing in pigeons plays a critical role in how they see the world.
But what ’s the veridical purpose behind this seemingly ridiculous motion ?
Related : Why Are There So Many pigeon ?
The1978 tread-wheel experimentgave us the first crucial insights into that question . And the study knock over one major supposal in the outgrowth : pigeon are n’t actually tail their heads . Instead , they ’re pushing them ahead .
Head-bobbing in pigeons plays a critical role in how they see the world.
When the researchers in that study review tiresome - motility footage , they receive that there were actually two main parts to a pigeon ’s capitulum movement , which the scientists called a " thrust " and a " hold " phase .
" In the ' thrust ' phase , the head is pushed forward , relative to the body by about 5 centimeters [ 2 inches ] , " excuse Michael Land , a life scientist at Sussex University in the United Kingdom who has studiedeye movementsin animals and humans . " This is be by a ' hold ' phase , during which the promontory is kept still in space , which mean that it moves backwards comparative to the forward - moving torso . "
What we see as a " bob " is actually the head slide smoothly forward and then waiting for the body to get up . We comprehend it as a bob because the motion unfolds so rapidly .
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" This happens on intermediate five to eight times a second as a pigeon is walk , " Aaron Blaisdell , a professor of psychological science who studiesanimal cognition , including that of pigeons , at the University of California , Los Angeles , told Live Science . " That ’s fast enough that , for us , we do n’t process it as the literal event unfolds and our minds treat it like a British shilling . "
So , all this time we ’ve been ridiculing pigeon for their quirky gait , and it turns out we were just witness it the ill-timed way . And the cause why pigeons practise this behavior , it turns out , is all aboutthe way that these birds see the world .
Visual processing
The researchers in the landmark salt mine experimentation find that if a pigeon ’s optical surroundings stay relatively stationary around the bird as it strut on the treadmill , the animal ’s headspring did n’t bob . Through rearward logic , this led to the key find : question - thrusting assist pigeons to stabilise their view of the moving human race around them .
" Keeping the head still in distance during the ' clutches '' phases means that the image will not be blurred by motion , " Land say .
In other words , a stationary foreland gives the bird a minute tovisually processits surroundings while it waits for its moving dead body to catch up ; it ’s like hitting pause on the movement for a fraction of a instant . This maneuver is utile because it " enable them to see potential food for thought — and possibly , enemies , " Land said .
If pigeons ' heads be active at the same footstep as their consistence , " they would have trouble restrain a unchanging image of the world on their retina , " Blaisdell explained ; the surrounding scene would swim by in a puzzling fuzz .
Blaisdell also apportion an adorable anecdote : During research in his own research laboratory , when he picked up a pigeon and walked forward with it , the bird still bobbed its drumhead , because the macrocosm was still moving around the pigeon even though the animate being was n’t displace of its own agreement .
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This visual trick is n’t just a quirk of pigeon life . Humans do a version of this too , except that instead of move our head , we employ rapid , jerky movements of our eyeballs to help fix our vision as we move through space .
" Our eyes do n’t move swimmingly and incessantly . They in reality jump from one shoes to another , " Blaisdell said . These item-by-item campaign are calledsaccades , " and once [ the centre ] reaches the end point of a jolt , it cling for a short duration , long enough to stabilise the image of the world on the retina so that we can process it , " he added .
In an uttermost form , this is the flick movement you see in someone ’s eyes as they watch the scenery unfolding outside the window of a fast - moving string .
Pigeon ’s eyes can move around like ours , but the birds also have more - peregrine mind than man do , so it makes horse sense that they ’ve evolved head teacher - thrusting as a more efficacious vision - stabilizing tool .
Bob, bob, bobbin' along
Pigeons may be the best - know birds for this trait , but they are n’t the only one that seem to be furrow along to an internal beat . " Most ground - feed chick do head - bob , " Land tell .
Chickensdo it , as do bird like herons , storks and crane . A heron lurches its head forward to nail its fair game , then play its body in line with the imposingly stationary head word ; this is the slow - motion variant of what a pigeon is doing , Blaisdell said .
He also provoke an interesting , and risible , idea . Birds are basically modern - day dinosaurs , and they divvy up much in mutual with their nonextant dinosaur full cousin . late discoveries have shown that many dinosaurs , evenTyrannosaurus male monarch , had feathers . " So , founder the commonalities between innovative shuttle and dinosaur , I inquire if dinosaurs did head - bob , too ? " Blaisdell say .
Of of course , that ’s saturated speculation , he cautioned . But it does leave us with the range of a function of aT. rex , tooth stop , its head bopping wildly as it runs frantically about .
Originally published onLive Science .
