National Geographic News
A New Caledonian crow.

New Caledonian crows are known to make tools in the wild, something that very few animal species do.


Virginia Morell

for National Geographic

Published April 3, 2014

New Caledonian crows are known for using tools in the wild. A team is investigating the cognitive abilities of these crows, which live on the archipelago of New Caledonia in the southwest Pacific Ocean, 750 miles (1,200 kilometers) east of Australia.

It was there, on the island of Grand Terre, that Sarah Jelbert, a doctoral student at Auckland University in New Zealand, and her colleagues tested the crows' understanding of cause and effect by presenting them with a test straight out of Aesop's Fables.

In one fable, "The Crow and the Pitcher," a thirsty crow can't reach the water at the bottom of a pitcher, but then begins to drop one pebble after another into the vessel. Slowly, the water rises to the top, and the bird gets its drink. How did Jelbert's New Caledonian crows measure up when presented with a similar test?

The scientists recently published their results in PLOS One. National Geographic caught up with Jelbert by phone to ask her more about the study and these smart birds. (See "Crows Have Human-Like Intelligence, Author Says.")

Why did you choose to work with New Caledonian crows?

They make tools in the wild, something that very few animal species do. They make tools out of sticks and shape them with their beaks to form a hook on the end. And then they use their sticks to lever grubs out of holes in rotting logs.

The grubs are fat and gel-like, so if they just poked a stick into them, they'd end up popping them and would have only a horrible mush of grub. But by using the hook on the end of their stick, they can lift them out.

We actually have a go at this ourselves at times. We have to collect the grubs for our work; we use them to catch the crows. Most of the grubs are inside the logs, and we have to hack them out with machetes. It's one of the more disgusting parts of the job. (See "Crows Better at Tool Building Than Chimps.")

The birds also make a tool from Pandanus leaves; it's a small bush that grows something like a palm. They use their beaks to snip into the side of a leaf, and then rip it up about 10 to 15 centimeters [4 to 6 inches], and snip it off at the top. The Pandanus leaves have natural barbs on their edges, so they make great tools. The birds use them to drag out insects that live beneath leaf litter.

What else can the crows do that surprises people?

We're still getting our heads around all they can do. One interesting thing: They don't use their tools just to get food, but [also] to investigate things they find that are scary, like a plastic snake in a box. They'll poke it first with a stick to see if it is dangerous.

What's your experimental setup like? You're working with wild crows?

Yes. We have a large aviary on Grande Terre. We set up nets in the wild, and will catch 6 to 12 birds, and bring them back to the aviary where they're nicely fed and cared for. We keep them for three months, and then return them to the wild so they can carry on with their lives.

How did you come up with your idea to give the Aesop's Fable test to the crows?

Our study was based on the fantastic work of two other researchers, Christopher Bird and Nathan Emery. [They showed that rooks would use stones to raise the water level in a tube so that they could reach a worm.] Dropping stones into water isn't something New Caledonian crows do in the wild; no animal does. But it is also a completely natural thing, and so is a fair test of animals' cognition.

We trained six crows to drop small stones into tubes. And then we gave them different tests to see how much they understand or can learn about the cause and effect of water displacement. Would they understand that dropping stones into water in a tube [to get a piece of meat to float to the top] is different from dropping them into sand in a tube? Or that hollow objects have a different effect from solid ones?

They did very well at four of the six tests, where they were able to apply their natural understanding of cause and effect and the properties of objects. They understood that solid objects sink and hollow ones float, for instance, and that it doesn't make any sense to drop stones into sand. But they were incredibly poor at the counterintuitive test, which involved a U-[shaped] tube; they had to infer that there was a connection between the two tubes, but none of them could do this.

And what do their successes and failures at these tests tell us about the cognitive abilities of New Caledonian crows?

We're trying to understand the cognitive mechanisms of animal minds, and to do that you need to look at tests that animals can pass and those that they fail. In human psychology, researchers have discovered that the way people make mistakes is often most informative about how they think. The errors give away how they are solving problems. Is this true for animals, too? Or do they have a completely different way of conceptualizing problems? By looking at the errors the crows make, we may get a better understanding of how they successfully solve problems.

Are the New Caledonian crows that you've used in your experiments putting what they've learned in your aviary to use in the wild?

Well, I hope so [laughs]. But we normally don't see them again after we set them free. We go to new areas to catch new birds.

Joyce Oliveras
Joyce Oliveras

On my opinion crows are very intelligent! I once heard a story that a group of crows destroyed a whole car!!

Melissa Huang
Melissa Huang

Someone might think crows are stupid and even evil because they're black. I don't think that is right. In fact, crows are much BETTER than some of us. They're also more clever. Animals are our friends. Animals are as important as human beings on Earth. 

Anyway, to protect the Earth is our duty. We get almost everything from the Earth but we are destroying it everyday. In a word, we should be good to the animals but not  to complain them or even hurt them.

  I love bird. I love animals. I love the Earth. To protect the Earth means to protect our selves. We've done too many bad things to the Earth. We might be PUNISHED(of course by the Earth) in the future

If you have the same idea as me, you can send e-mails to  Shall we be e-friends?

Vangie Rich
Vangie Rich

We live in the mountains at 4118' among a wonderful assortment of wild life who visit our yard, from Black bears, fox, Bobcats, 'Coons and 'Possum to a large number of birds including crows. One crow in particular seems to be the leader of the pack. He comes to our yard scouting for food and when we have food to offer he calls the rest of the flock to come and feast. We have named him "Carl" and yes, he knows his name! Once in a while Carl will selfishly invite himself to dine alone, especially if lunch includes fruit and nuts. He hasn't taken food from my hand yet but he gets almost within reach and will flip his head as if to say, "put it down and I'll come closer!" I know farmers hate the crows but they are so amazing we can't help but to appreciate them.

Vince Williams
Vince Williams

I have a number of videos and photos from my numerous hand-feeding encounters with 4 species of birds: red-breasted nuthatch, American robin, ruby-throated hummingbird and many black-cap chickadees. 

I can provide many instances of the intelligence of birds. I noticed that a chickadee always flew to my hand precisely at 10 a.m. each morning so I informed the local newspaper. They sent a photographer who set up a bit prior to that time. I told him he would only have 2 seconds to get the shot, so he had his camera ready. At exactly 10 a.m. my bird friend arrived, the photographer clicked, and the photo appeared in the local paper. 

Another chickadee always enjoyed waking me in the early evening when I was napping. He would fly and flutter close to my face to wake me. Black walnuts are their favorite foods. 

An American robin returned for four years and would fly to me and sit on my lap for extensive periods of time to eat meal worms. 

A hummingbird flew to a feeder in my hand for food. 

A red-breasted nuthatch loved to fly to my hand for meal worms.

For some reason wild birds seem willing to trust me. There's an ability for them to distinguish among humans as to that acceptance. An intelligent sense to know and identify people is evident. I'm not sure how good you are at telling similar specie birds apart, but that's one of their obvious mental skills.

Dwayne LaGrou
Dwayne LaGrou

Thats incredible!!! We know that some birds are smarter than others, And that some can actually talk to us, But we never asked ourselves if they actually UNDERSTOOD what was going on. It would be interesting to see if a talking bird could be tested to see if they understand what they are saying or are simply copying our language!?

Maybe for your next study!

Ed Iverson
Ed Iverson

@Dwayne LaGrou - With parrots, there is ample evidence that they understand the meaning of words and phrases that their human companions routinely speak to them, and will use those words and phrases in contextually appropriate ways.  Here are two examples involving my own African Grey, Gandalf:

One phrase Gandalf often hears from me is "whatcha doin'?" whenever he's messing with something.  He also picked up the wolf whistle as a sound meaning "approval".  I make something called "glop" as a standard part of their diet (a mix of veggies, rice, nuts, pureed squash or sweet potatoes).  One time the glop supply ran out on a Thursday, and I didn't feel like making more until the weekend, so I got some asian stirfry takeout, thinking it would make an ok substitute for a couple of days.  On Thursday, he ate it with some interest, as something new.  On Friday, he nibbled at it but was obviously losing interest.  On Saturday morning, he wouldn't touch it, and seemed  irritated that his glop wasn't available, so I went to the store, bought the ingredients, and came home and started mixing it.  He was perched above me on a cabinet, intently watching me work with the glop.  He hopped down onto my shoulder, looked me in the eye and said "whatcha doin'?"  I said, "well, I'm making food for Gandalf."  He gave a long, loud wolf-whistle.  I said, "oh, are you hungry, you want some glop?"  Another long, loud wolf-whistle.   Clear communication going on there.

Another time, when he was young, he had a bad habit of pinching my fingers too hard with his beak (he was barely over a year old at the time, and we were still adjusting to each other).  When he did that, I would say "WHAT ARE YOU DOING?!" in my angry voice (from the bird's point of view, that is a different sound than the inquisitive "whatcha doin'?").  He was sitting behind me on the back of my chair, and I absently reached back to give him a scratch.  He pinched my finger hard.  I had a wet paper towel in my hand, and exclaimed "Ow!" and wapped him with the wet paper towel.  I heard my own angry voice behind me saying "WHAT DOING?!"  Definite indignation.

There are many other examples.  When Gandalf is on my shoulder, if I intend to move or change posture, I say "Hang on, Gandalf!", and I feel his foot grab my shirt collar.   I have another parrot, a senegal named Cricket.  The two birds know each other's names - if I call one's name, that bird responds but not the other.   If the birds are in separate rooms and I ask Gandalf, "where's Cricket?", he calls for her.  If I ask Cricket "where's Gandalf?", she goes looking for him, and will often bring him back to me (how she convinces him to come is a mystery). 

Not everything they say is meaningful - a lot is just repetition.  But they learn the meanings of words and phrases that identify objects or actions that are relevant to them - words for foods, water, toys, phrases that indicate it's time to go in their cages, or time for a shower,  or that I'm leaving for awhile, etc.  Words for things that aren't relevant to a bird mind are not used meaningfully, those are just repetition if used at all  (I've never explicitly tried to train my birds to repeat things, I just let them pick up whatever comes naturally. )

m p.
m p.

@Ed Iverson @Dwayne LaGrou

Care to share yr Glop recipe? I also have a grey.

Dwayne LaGrou
Dwayne LaGrou

Thank You for taking so much time to tell me about your bird "Friends". It's so cool to finally find out that the so called "Dumb Animals" have so much empathy and understanding that were thought to be "Human Only" traits. Just think how much more we will learn in the future?! Thanks again for your time and effort.



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