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Budgerigar (Parakeet) Study Reveals how Birds Avoid Crashes in Tight Quarters

OilbirdsIf you observe wild birds, you’ve no doubt marveled at their ability to fly through dense brush without touching a single branch.  In NYC, I’ve twice been surprised to see pigeons flying at full speed through amazingly tight spaces when pursued by Red-Tailed Hawks.  Bats utilize echolocation to perform similar feats, but with few exceptions (i.e. the Oilbird, please see below), birds lack this adaptation.  So how do they do it?  According to a recent study (Current Biology, Oct., 2011) at Australia’s Vision Center and the University of Queensland, some species rely upon vision alone.

“See-Compare-Adjust Course”

Researchers worked with Budgerigars (Parakeets) that had been trained to fly an indoor course that allowed for careful monitoring.  They were able to show that the birds used their vision to sense and compare the speed at which they passed background images, and then adjusted their flight path accordingly. 

As birds move forward, objects that are near seem to speed by quickly; objects that are further away appear to go by at a slower pace.  So, as a bird gets closer to an object, the eye nearest it will perceive that object to be moving faster than objects seen by the other eye.  The bird will then veer away from the nearby obstacle to avoid a crash.

This “sounds good on paper”, as they say, but what amazes me is the speed at which birds perform these maneuvers.  Add to that the complex, ever-changing environments and wind conditions to which birds in flight are subjected, and you’ll realize what skilled navigators they are.

Monocular vs. Binocular Vision

Budgerigars and most other birds have monocular vision – that is, eyes that are set widely apart on either side of the face.  This orientation is ideal for flying as described above, because each eye is usually seeing a different object.

Hawks, herons and certain other predatory birds have, in common with us, binocular vision…forward facing eyes that can focus on a single object simultaneously.  This allows for effective hunting.  I wonder if they are able to navigate with the same efficiency as Budgerigars (perhaps not – I have observed several hawk-crane-heron accidents).  Most fly in relatively open environments, but Sharp-Shinned Hawks and some others are known for pursuing prey through dense tree cover.

Specialized Navigators: Owls, Oilbirds and Swiftlets

Barn OwlBirds of all kinds have other amazing flight adaptations that enable them to survive.  The nocturnal, cave-dwelling Oilbirds and Cave Swiftlets can fly and feed in complete darkness, aided by a form of echolocation similar to that used by bats.

In certain owls, one ear is located slightly higher on the head than the other.  Sound reaches each at a slightly (very slightly, I imagine!) different time, and can be used to triangulate the sound’s source.  By triangulation, Barn Owls can locate and capture an unseen mouse that is over a football field distant from them!  Perhaps this ability explains why Barn Owls are among the most widespread of all birds of prey…I’ve observed them several NYC neighborhoods, and they nest on every continent except Antarctica.

 

 

Further Reading

Migration and other amazing navigational feats

Video: Wild Budgies in flight

Budgerigar Migration: interesting facts and photos

 

Oilbirds image referenced from wikipedia and originally posted by The Lilac Breasted Roller
Barn Owl image referenced from wikipedia and originally posted by Stevie B

About Frank Indiviglio

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I believe that I was born with an intense interest in animals, as neither I nor any of my family can recall a time when I was not fascinated by creatures large and small. One might imagine this to be an unfortunate set of circumstances for a person born and raised in the Bronx, but, in actuality, quite the opposite was true. Most importantly, my family encouraged both my interest and the extensive menagerie that sprung from it. My mother and grandmother somehow found ways to cope with the skunks, flying squirrels, octopus, caimans and countless other odd creatures that routinely arrived un-announced at our front door. Assisting in hand-feeding hatchling praying mantises and in eradicating hoards of mosquitoes (I once thought I had discovered “fresh-water brine shrimp” and stocked my tanks with thousands of mosquito larvae!) became second nature to them. My mother went on to become a serious naturalist, and has helped thousands learn about wildlife in her 16 years as a volunteer at the Bronx Zoo. My grandfather actively conspired in my zoo-buildings efforts, regularly appearing with chipmunks, boa constrictors, turtles rescued from the Fulton Fish Market and, especially, unusual marine creatures. It was his passion for seahorses that led me to write a book about them years later. Thank you very much, for a complete biography of my experience click here.
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