Why clever crow is no bird brain

Oct 09, 2012
A crow drinks water at the Alipore Zoo in Kolkata. Biologists on Tuesday said they had figured out how the New Caledonian crow, a bird famed for using tools, does its party trick.

Biologists on Tuesday said they had figured out how the New Caledonian crow, a bird famed for using tools, does its party trick.

Corvus moneduloides, a native of France's South Pacific territory of New Caledonia, is one of the stars of the avian world.

It uses its beak to craft complex tools from sticks, leaves and other material and then inserts them into deadwood or vegetation to fish out insects and other food.

Researchers led by Jolyon Troscianko of the University of Birmingham in central England used an ophthalmoscope video camera to record field of view and eye movement as three wild-caught birds examined a baited tube.

The bird's eyes are more forward-positioned, rather than sideways-positioned, which gives it exceptional "binocular overlap," they found.

This is the area that is viewed by both eyeballs, and is important because it helps the brain judge the distance of nearby objects.

In , the binocular overlap is 61.5 degrees, which is at least 23.9 degrees greater than in non--using species of that the researchers also examined.

Added to this is the crow's unusually straight bill, the investigators found.

With it, the bird can get a firm grip on a tool and bring its tip into its field of binocular vision.

"These features enable a degree of tool control that would be impossible in other corvids [crows], despite their comparative ," says the study, published by the journal Nature Communications.

Dolphins, elephants and other birds are among non-primates that have been found to use tools. But the New Caledonian crow occupies a privileged place because its features are so specifically adapted for tools, says the study.

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User comments : 6

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B__
1.3 / 5 (3) Oct 09, 2012
In humans the role of binocular vision is highly overrated. We gain much of our structural sense of the world from light and shade, not stereo vision. Many people don't even perceive 3D structure from stereo vision well in the absence of other cues.
vega12
5 / 5 (2) Oct 09, 2012
In humans the role of binocular vision is highly overrated. We gain much of our structural sense of the world from light and shade, not stereo vision. Many people don't even perceive 3D structure from stereo vision well in the absence of other cues.

Yes, for static images that could be a big factor, but try catching a ball with only one eye open and you will quickly feel just how much stereo vision is necessary. If it wasn't so important, there wouldn't be such a clear difference between predator and prey eye positioning in nature.
VendicarD
not rated yet Oct 10, 2012
B is smarter than those behind the 3d TV flop.

"We gain much of our structural sense of the world from light and shade, not stereo vision." - B
vh16
not rated yet Oct 10, 2012
These findings don't explain some experiments related to Corvus moneduloides cognitive abilities, including this one:
/news/2012-09-crows-infer-actions-hidden-agent.html
dogbert
not rated yet Oct 10, 2012
Stereo vision is certainly a plus, but is clearly not necessary to judge distance/speed. Drivers with only one functioning eye can drive quite well, judging accurately the speed and distance of other cars/pedestrians.

Our brains can use apparent size and change in apparent size to determine distance and speed. We can also construct a feeling for 3D by observing objects pass behind other objects and reappear.

Of course, there are people with two good eyes who cannot accurately judge speed and distance.
vlaaing peerd
not rated yet Oct 10, 2012
that's not entirely correct. One-eyed drivers may not have 3D stereovision but they are perfectly able to judge distance by the perceptive size of the object in their vision. You know how large a BMW is by experience and use this information to extrapolate the apparent distance of that car. Don't underestimate the ingenuity of the human mind and body, it's able to compensate for almost everything - even a missing brain half!