Acorn woodpeckers defend their larder

Reader Michael sent this National Geographic video about acorn woodpeckers (Melanerpes formicivorus) and a larder tree near the Grand Canyon. As I suspected, they drill each hole to fit a specific acorn (how else could the food remain securely wedged?), but then how do they drill a hole for a specific acorn without having it in their mouth? This is a mystery that, I hope, readers will solve.

At any rate, you can see they cooperatively guard the food supply (are the birds related?), and you can see them driving off a marauding squirrel.

13 Comments

  1. yazikus
    Posted June 18, 2019 at 3:37 pm | Permalink

    Wonderful! These past couple of years living in the forest have increased my appreciation for birds so much. They are curious, busy, noisy & social (okay, sometimes really noisy!).

  2. Randall Schenck
    Posted June 18, 2019 at 3:44 pm | Permalink

    Amazing stuff. I would guess maybe not related to each other. Have no idea. The holes are all slightly different so it’s a matter of finding the right hole for the nut. Once you have all the holes I suppose they get to use them year after year. Maybe the birds that made the holes are long gone?

    • Posted June 18, 2019 at 6:21 pm | Permalink

      That seems to be it, as shown in the very good video.

    • rickflick
      Posted June 18, 2019 at 7:31 pm | Permalink

      The narrator mentions the extended family is involved in keeping the larder safe. I think it’s mostly kin selection at work.

  3. Roger
    Posted June 18, 2019 at 6:34 pm | Permalink

    It looked like the first little guy was trying out several holes before he found a one to his liking.

  4. Stephen Barnard
    Posted June 18, 2019 at 9:21 pm | Permalink

    ” As I suspected, they drill each hole to fit a specific acorn (how else could the food remain securely wedged?), but then how do they drill a hole for a specific acorn without having it in their mouth? This is a mystery that, I hope, readers will solve.”

    In their spare time they drill a bunch of holes with a size and shape variation roughly matching the variation of the acorns. When they have an acorn to store, they search for an appropriate hole.

  5. Joe Dickinson
    Posted June 18, 2019 at 9:22 pm | Permalink

    I’ve always assumed that a larder tree is maintained and defended by an extended family, but I don’t have specific evidence for that. It just seems right from the perspective of kin selection theory.

  6. Jenny Haniver
    Posted June 18, 2019 at 9:30 pm | Permalink

    From my reading, it seems that the acirb woodpeckers don’t drill each hole to fit a specific acorn that they’ve already chosen, but drill scads of holes of acorn size before gathering them, and then take a specific acorn and try it out in various pre-drilled holes until they find one that’s just right. My reading also says that as the acorns dry, they shrink and so the birds must find another hole that fits, and keep moving the acorns around as this happens. Sometimes they drill new holes but the old ones are re-used time and time again, which makes sense to me.

    • Jenny Haniver
      Posted June 18, 2019 at 9:37 pm | Permalink

      “acirb” no, not a new species, a typo.

  7. ThyroidPlanet
    Posted June 18, 2019 at 11:24 pm | Permalink

    This is amazing – somehow I think a pic of these came through my channels last week… was it a low-grade viral pic?


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