Those Magnetic Neurons Birds Use to Steer? They're Not Neurons, and Aren't For Steering.

By Veronique Greenwood | April 12, 2012 2:53 pm


What’s the News: One of the leading theories explaining why birds can travel thousands of miles each year without getting lost is that they are equipped with an internal compass on their beaks: iron crystals in cells there could be orienting to the Earth’s magnetic field, sending a message to their brains that helps them steer.

It turns out, though, that those beak cells, which had been previously identified as neurons capable of sending such a message, aren’t neurons at all. A new study shows convincingly that those iron-bearing cells are macrophages, immune cells that could never play that role. Birds’ magnetic navigation skills must be coming from somewhere else.

What’s the Context:

  • The magnetic beak neuron theory, proposed in 2007, had already been in doubt; a study in 2009 found that while certain pigments in birds’ eyes were required for them to respond to magnetic signals, screwing with the beak “neurons” didn’t seem to affect it. This team, though, has put the nail in the coffin with a series of detailed histological, or staining, dissections of the beaks of pigeons.

How the Heck:

  • While the 2007 study reported that the cells were distributed evenly on either side of the beak in a pattern that suggested they were neurons, this team found that they were not.
  • Moreover, different birds, even birds of the same type and sex, had wildly different numbers of the cells, a red flag that they probably weren’t involved in an ability that the birds had in common.
  • Stains that usually cling to neurons made no mark on the cells, while macrophage stains did, and when the team looked closely at their structure with an electron microscope, they noticed that they appeared to be engulfing neighbor cells, something macrophages do as part of their work but neurons don’t.
  • Just to hammer it home, they found cells that looked exactly the same throughout the pigeons’ bodies, in areas with no known connection to navigation. The cells even appeared to be responding to an infection in one pigeon, just as macrophages would.

The Future Holds: So where are birds getting their uncanny powers? The theory put forth by that 2009 study, that a chemical reaction between light and pigments in the eye is involved, is currently the best lead. Read more about it here.

Reference: Treiber, et al. Clusters of iron-rich cells in the upper beak of pigeons are macrophages not magnetosensitive neurons. Nature (2012). doi:10.1038/nature11046

Image courtesy of crossbone80 / flickr

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  • Shiva Steve Ordog

    Actually, although stated here that a chemical reaction between light and pigments in the eye is involved, is currently the best lead for how birds navigate home, Rupert Sheldrake has a much more plausible explanation involving morphic fields. The book Morphic Resonance explains these fields well. For another fascinating book on animal behavior, see Sheldrake’s “Dog’s who know when their owners are coming home.” And finally, if you think this is non-scientific hooey, check our Sheldrake’s work “The Science Delusion” for a great explanation of how materialist science has blinders on.

  • Geack

    That Sheldrake stuff is non-scientific hooey.

  • Cody

    Shiva Steve Ordog, “materialist science has blinders on” doesn’t really make a lot of sense: in all science, evidence is king, and when it comes to non-material phenomena, physicists have dedicated formidable resources of time money and energy to probing reality for causal mechanisms—material or not. Our theories describing both material and non-material phenomena are now so precise that there is very little room for the sorts of claims Sheldrake appears to be making. The bar for evidence is set so very high—in the absence of extraordinary evidence his claims are relegated to the bins of “non-scientific hooey”.

  • Shiva Steve Ordog

    I invite you to investigate Sheldrake’s experiments and data and see for yourself.

  • Adasif

    “Our theories describing both material and non-material phenomena are now so precise that there is very little room for the sorts of claims Sheldrake appears to be making.”

    That’s a rather high claim, to claim that we are at some scientific high point and the only thing we need is to fill in some detail. This is arrogance at its finest and claiming that we have all the main elements set up is scientifically unsound.

    Actually this is a very typical “blinder”. To believe that we have all the equipment in place and now we can record everything. You are claiming something you can’t show evidence for, which is the same claim you admonish Sheldrake for. Only difference is that he shows data that shows something unaccounted for(well, you can always say it doesn’t, that’s why we have religion). You could maybe learn some real science from him despite that you disagree with his theories(which haven’t been proven, but there is evidence for it. Much like Ian Stevenson’s work).

    You are one of many pseudoskeptics who have extraordinary claims much like the people who believe they have seen ghosts, UFOs, or Bigfoot. You have turned science into a religion and for that you should be ashamed. You are no better than the theists of the dark ages. Science is a method of inquiry, not religion, and it is always evolving and discovering new things.

  • Silly

    Successful pseudoscience troll is successful

  • Rauf Sheldrake

    Sheldrake is only trying to explain the parts which science currently cannot explain though it could be possible in the future. But he is accumulating numbers behind him into a substantial critical mass of believers in how Nature and Nature of Reality is structured where all the experiments of Science are conducted. It certainly is not a religion but a careful observation, inquiry and a study perhaps inductive reasoning more than deductive like in the good old days but essentially part of modern Science.

  • adam

    The article linked to says that birds require light for the cryptochrome to function. However, many passerines successfully travel at night during migration when light is not present. How is that accounted for?

  • WildaBob

    Maybe the location of the macrophages in the beak is not coincidental and does play a role — like the end of rifle it serves as a guide to align the eyes — so the macrophages are used as an invisible (to us) alignment tool while somehow seeing the magnetic fields of the earth?

  • Wes

    It seems to me that Sheldrake discussed cases where birds were displaced from their normal migration routes and still got there, seeming to require something more than just a compass. In the same way, early sailors required more than a compass and used astronomical data to correct for wind and sea displacement. No one has yet explained what long range migrating birds and turtles use. When the science fundamentalists (strict materialists) prove how it’s done, then they can criticize Sheldrake if he’s wrong. All we have now is dueling theories, and some very unscientific personal attacks.

  • Jeff

    Adam, I have never observed a night even under the darkest conditions, when there was no light.

  • Matt L

    “Morhpic Fields” are a fake phenomemon created by Terry Pratchet in his Discworld novels, used to explain why ghosts of things tend to look like what they were in life and to put some sense of danger into shapeshifting/mind control/mind borrowing.

  • Kennita

    Dogs can hear sounds too faint or high-pitched for people to hear one explanation for some of the knowing-master’s coming-home phenomena). Perhaps birds are using light too faint (or in a different spectral range) for humans to detect as part of the input to their cryptochrome.

  • Karl Kindt

    The dogs that are studied in his experiments could not “hear” at the huge distances involved in the study. Hence you obviously have not bothered to read the scientific data in his book. In any case, whatever you want to call the ‘fields’ that are used by animals to detect various aspects of reality we can’t detect they obviously are detecting in ways we can’t and through a means we can’t figure out as of yet. But someone who is a pure materialist – ie that there is just matter and who is a monist – there is nothing but physical stuff – no stuff made of something that is non-physical but interacts with the physical – someone who holds to this religion – will not be able to comprehend or bother to research other possibilities. That is why Sheldrake goes where the evidence leads him and others who reject non-material reality – will not follow the evidence but try to conjecture solutions that fit with their religion.

  • Richard Nadeau

    What Sheldrake does is not science at all. His beliefs are not altered when the data contradict them — he assumes the data to be wrong. Richard Wiseman’s work with him showed that Sheldrake’s work is driven by his spiritualist, anti-materialist beliefs. Belief in a non-material world is just that, a belief, for there is no evidence for it so far. If evidence ever does appear, fine, we’ll accept it. But so far, all we see are logical fallacies and the god of the gaps argument.

    Spiritualists, like Sheldrake, who denigrate materialists for being “religious”, seem to be lacking the gene for irony-recognition.

    Anyway, real scientists continue to chip away at the great mysteries and discover the wondrous (and so far, natural) workings of the universe.

  • Philippa Doran

    Our godwits fly non stop from Alaska to New Zealand, and end up at the same place here.

    Turtles can find the same beach to lay their eggs.

    Even the Monarch Butterfly migrates in America, and hundreds end up in the same trees.

    What would these three different creatures have in common?


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