Those clever corvids

NOT so long ago, the idea that birds might possess some form of what we call intelligence seemed quite ridiculous. Yet this view has changed dramatically in recent years, with numerous studies showing that some bird species are capable of complex cognition. Members of one family of birds in particular – the Corvidae, which includes crows, rooks and ravens – have an ability to make and use tools which is at least as sophisticated as that of chimpanzees.

Two new studies, published this week, provide yet more demonstrations of the remarkable cognitive abilities of this group of birds. One shows that Caledonian crows can use up to three tools in sequence to obtain food, the other that rooks can use stones to raise the level of water in a vessel in order to bring a floating worm into reach.

This study, by Joanna Wimpenny and her colleagues at the University of Oxford’s Behavioural Ecology Research Group, is the first demonstration of spontaneous sequential tool-use in a species other than humans. Sequential tool use is indiciative of an ability to plan ahead, but more research is needed to establish whether this behaviour is actually the result of rational planning, or merely of a process called chaining, whereby a series of stimuli evoke a sequence of responses. (However, the scrub jay, another member of the corvid family, has been shown to be capable of planning for the future.) These findings are published in the open access journal PLoS One.

The second study, by Chirstopher Bird and Nathan Emery of the University of Cambridge and Queen Mary University of London, respectively, is published today in Current Biology. Unlike crows, rooks have not been observed using tools in the wild, but this study clearly demonstrates that they are capable of solving a complex problem. The rooks used in the study also quickly learned to use large stones instead of small ones, and that sawdust cannot be manipulated in the same way as water. 

The problem solved by the rooks is analagous to the one in Aesop’s fable, The Crow and the Pitcher:

A Crow, half-dead with thirst, came upon a Pitcher which had once been full of water; but when the Crow put its beak into the mouth of the Pitcher he found that only very little water was left in it, and that he could not reach far enough down to get at it. He tried, and he tried, but at last had to give up in despair. Then a thought came to him, and he took a pebble and dropped it into the Pitcher. Then he took another pebble and dropped it into the Pitcher. Then he took another pebble and dropped that into the Pitcher. Then he took another pebble and dropped that into the Pitcher. Then he took another pebble and dropped that into the Pitcher. Then he took another pebble and dropped that into the Pitcher. At last, at last, he saw the water mount up near him, and after casting in a few more pebbles he was able to quench his thirst and save his life.

Little by little does the trick.

Bird and Emery even suggest that the ancient Greek story-teller may have based his tale on a real observation. But in folklore, all members of the corvid family are referred to as crows, so if Aesop did indeed observe this behaviour, it may have been a rook that he saw.

For more on the cognitive abilities of birds, and more vids of crows doing incredibly clever things, see this post about avian intelligence.

Wimpenny, J. et al (2009). Cognitive Processes Associated with Sequential Tool Use in New Caledonian Crows. PLoS ONE, 4 (8) DOI: 10.1371/journal.pone.0006471.

Bird, C.D. & Emery, N. J. (2009). Rooks Use Stones to Raise the Water Level to Reach a Floating Worm. Curr. Biol. DOI: 10.1016/j.cub.2009.07.033.


7 thoughts on “Those clever corvids

  1. The crows in my garden seem to know that my cat is an enemy of theirs, judging by the way they dive-bomb him whenever they see him until he runs away.
    Never seen another bird do that. One once dive-bombed me, actually, came about a foot from my head…

  2. Crows are well-known in the world of amateur birding for their intelligence. Crows not only dive-bomb cats, but will gang up on then. They, along with jays and mockingbirds, are the look-outs for backyard ecosystems, uttering loud grating cries whenever a threat (such as a cat) comes into the yard.
    But they can also be attacked themselves. Many a birder has seen smaller birds, often nesting couple, band together to drive a crow away from a particular tree or feeder.
    The video of the rook with the water tube was absolutely delightful. Had the bird developed that behavior over time, or was that a novel situation for it?

  3. I hand feed my scrub jays, the leader of which has become my pal. His name is “Bingo” because all I have to do is sit down in my chair on the patio with my bag of peanuts and “Bingo!” he’s right there. Ready for a handout. He’ll pick one, put it in his beak to weigh it, and if it doesn’t meet his standards, he’ll put it down and go for a second. Then he’ll lift each and compare them (I assume looking for the meatiest/heaviest one then takes off across the street to bury it before coming back to beg for another. Meanwhile, all the other 25 or so are up in the surrounding pine trees watching him do this and making sure Bingo can’t see them as they swoop down to pick up the peanuts I toss on the ground. I had to feed them when Bingo isn’t looking, because he’ll actually attack them (evidently he’s the King of the families) and chase them back to their nests.

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