Aesop Was Right! Birds Use Rocks to Raise Water Level

By Eliza Strickland | August 6, 2009 3:21 pm

A quartet of clever rooks have provided evidence that one of Aesop’s fables could have a basis in fact. The tale in question tells the story of a thirsty crow. The bird comes across a pitcher with the water level too low for him to reach. The crow raises the water level by dropping stones into the pitcher. (Moral: Little by little does the trick, or in other retellings, necessity is the mother of invention) [AP]. In the new lab experiment, four rooks each dropped stones into a clear plastic tube, which raised the water level high enough to bring a floating worm within reach.

Rooks and crows are both in the corvid family, which researchers say rivals the great ape family for intelligence and tool use–the only other animal that has performed a comparable task was an orangutan, who spat into a tube to gain a floating peanut. Says study coauthor Nathan Emery: “We have performed a large number of studies on both corvids … and apes, and have found that the crow’s performance is on a par or often superior to apes. However, it is not particularly useful to say that one species is more or less intelligent than another because often the playing fields aren’t even” [The Independent]. 

Rooks are not known to use tools in the wild, but have proven remarkably adept with them in labs: The same group of four birds previously fashioned hooks out of wires and used them to pull food-bearing buckets up through a glass tube. Emery says the new study “suggests that they can not only think through complex problems requiring the use of tools, but imagine the consequences of their actions without trial-and-error learning, and create novel solutions to these problems that have never been encountered before” [The Independent].

In the experiment, described in Current Biology, the rooks proved highly accurate, placing in only the precise number of stones needed to raise the water level to a reachable height. Instead of trying to get the worm after each stone was dropped, they apparently estimated the number required from the outset and waited until the time was right [LiveScience]. And when given a choice of small and large rocks to use the birds chose to use the bigger stones, suggesting that they knew those rocks would displace more water and bring the tasty worm up faster.

Related Content:
80beats: Not So Bird-Brained After All: Rooks Make and Use Tools
80beats: Mockingbird to Annoying Human: “Hey, I Know You”
80beats: Watching YouTube Videos of Dancing Birds for the Sake of Science
80beats: We Told You Chicks Are Good at Math: They Count, Add, and Subtract
80beats: One Giant Leap for Birdkind: A Magpie Looks in the Mirror and Recognizes Itself

Video: Christopher Bird

  • robot makes music

    “However, it is not particularly useful to say that one species is more or less intelligent than another because often the playing fields aren’t even.”

    I guess the same could be said about the human species.

    I <3 corvids. I want more to live near here.

  • http://LHRM@OPTONLINE.NET Louis HR Muller

    One morning when I arrived at work there was a mostly empty Burger King drink of around 24 ounces with the top on and the straw still in it. A crow kept lifting up the container by its bottom lip so that some of the remaining drink (soda ?) would drip out. When a small puddle would form, he would turn his head sideways so that the side of his beak rested on the blacktop and then lick up the puddle. I spent minutes watching him repeat the process several times. It would have been so great if I had had a camera.

  • Louis HR Muller

    On another occasion three crows were harassing a hawk. The hawk had landed with its prey on a lawn and the crows were preventing him from eating it or being able to fly off with it. The hawk was about the same size as the crows so they apparently felt safe. Since I was driving past on my way to work I wasn’t able to stay around to see how the situation was resolved.

  • ahrcanum

    How many rocks is Obama going to have to use to sell health care reform?

  • Thomas A.

    Um, ahrcanum… did you just call Obama a crow?

    That’s a very old and very unpleasant racial slur. Stop it.

  • Sally

    Hey, ahracanum, let’s just enjoy the awesomeness of the natural world, and not make everything political, okay?

  • Josh

    That rook attempted to get the worm after every rock, whereas the reporter claims that the rook did not do such, but ‘estimated’ the number of rocks needed.

  • Alex B

    congrats to ahrcanum for the most unnecessary, random, and intentionally provocative comment of the day

  • ahrcanum

    Thomas-, I did not call our President a Crow certainly with no intentional slur as the article refers to crows- which I have hundreds of to observe eating my corn on my farm which accepts no gov’t subsidy. Couldn’t help making the political connection as in Sally’s comment.

    My point generally being, that in President Obama’s quest to quell his thirst for bird brained socialism and insurance reform, he seems to be willing to throw rocks and do whatever he deems necessary to displace capitalism and own another industry. The automobile industry, the banking industry, soon the health care industry – just seems bird brained to me.

  • snaggy

    Get a grip, ahrcanum. Another right-winger who needs to turn everything into a political debate.
    Speaking as a Canadian, though, I think its more bird-brained to leave millions of citizens to die or suffer needlessly without health care. Contrary to current Republican fear-mongering, our health care system is cheaper, per patient, than American Health care. And wait times are not excessive (one coworker of mine saw his doctor for stomach pains, and within two weeks was tested, biopsied, diagnosed, and treated for stomach cancer, in Canada.)
    Do some research, neighbour, before you beak off.

  • Irv

    Ahrcanum – No matter what your reference was to towards Obama, can we just not mix politics in this for once. It’s nice to read things once in a while that have nothing to do with politics or any other issues. =)

  • Robert

    @ arhcanum, please keep your unrelated political commentary to the political forum.

    If you noticed Discover Magazine doesn’t have one, it’s because it’s about Science, not Politics.

    As to the crow estimating the correct amount of rocks, I wouldn’t bet on it. It probably dropped in rocks until it could see the worm was close enough to grab, then did so.
    (Not everything needs to be fully planned out to work.)

  • Brad

    People in Sydney used to place steel trash can lids over milk bottles to prevent crows from pecking through the foil and drinking the milk. I saw a film where a group of crows flew off with the lid which would have been too heavy for one, and then devour the milk!

  • —-Rocks—-


  • Christina Viering

    I love these studies!

  • festival music

    You got numerous positive points there. I developed a explore the matter and found nearly all peoples will accept your site.


Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!


80beats is DISCOVER's news aggregator, weaving together the choicest tidbits from the best articles covering the day's most compelling topics.

See More

Collapse bottom bar