02 February 2016

How some birds locate seed caches

Robert Krulwich explains:
Around now, as we begin December, the Clark’s nutcracker has, conservatively, 5,000 (and up to 20,000) treasure maps in its head. They’re accurate, detailed, and instantly retrievable.

It’s been burying seeds since August. It’s hidden so many (one study says almost 100,000 seeds) in the forest, meadows, and tree nooks that it can now fly up, look down, and see little x’s marking those spots—here, here, not there, but here—and do this for maybe a couple of miles around. It will remember these x’s for the next nine months...

When December comes... the trees go bare and it’s time to switch from hide to seek mode. Nobody knows exactly how the birds manage this, but the best guess is that when a nutcracker digs its hole, it will notice two or three permanent objects at the site: an irregular rock, a bush, a tree stump. The objects, or markers, will be at different angles from the hiding place...

In the 1970s, Stephen Vander Wall ran a tricky little experiment. He shifted the markers at certain sites, so that instead of pointing to where the seeds actually were, they now pointed to where the seeds were not...
The rest of the story and more details at the link.


  1. I like the first explanation in the comments: it's not that the birds remember thousands of sites but they have one or two rules for where they bury seeds. When it comes time to retrieve the seeds, they just apply those rules and dig. Most likely they'll find seeds.

    If this is an accurate assessment of the situation, it seems like it'd be easy enough to test. Just arrange an acre or two of habitat to conform to the rule in only certain places and see if the birds bury seeds contrary to the rule.

    I'm sure no one would object to disturbing habitat like this. ;^)

  2. I wonder how many of the unretrieved seeds germinate?

  3. I would guess a lot by the amount of tomatoes that grow far away from where I plant them. As an addendum to this information, a link from that page brought me to this fascinating article... http://phenomena.nationalgeographic.com/2015/07/28/seeds-that-defied-romans-pirates-and-nazis/

    1. There are quite a few good links on that page. If you enjoy Robert Krulwich' style, you might enjoy listening to some of the "Radiolab" podcasts.


  4. i leave out food scraps for the crows. when they are not hungry, which is most of the time, they take the food and hide it in the grass, snow, whatever. i have been told that the crows do remember where they hid this food, which i have been skeptical of. maybe it is true?


  5. This comment has been removed by the author.

  6. This is a somewhat impressive feat, but it is reported in a bit of a breathless tone. Most modern humans don't have to work on optimizing their brains for spacial navigation, but they do a lot of memorization.

    Exempli gratia: "The mystery here, the deep mystery, is how do they manage to store so much data in their heads?" said the human who has a vocabulary of more than 20,000 words composed of arbitrary sounds and a mapping of those sounds to sequences of 26 arbitrary symbols of arbitrary length in countless combinations. And that is just one small set of memorized data required to be a functioning human adult.

    Long story short, we discount our own feats of memorization because they don't feel like memorization to us.


Related Posts Plugin for WordPress, Blogger...