Science: Bird Migration
Monday, May 5, 2008; 12:00 PM
Washington Post science writer Rick Weiss was online May 5 at 12 p.m. ET to discuss new research that gives clues about how birds use the earth's magnetic field to navigate on migrations.
He was joined by Devens Gust, a researcher at Arizona State University.
Read about the research here: Molecular Action May Help Keep Birds on Course.
The transcript follows.
Rick Weiss: Rick Weiss: Hello everybody and welcome once again to the weekly Washington Post sience Web chat, where I am joined this week by Devens Gust, a chemist who has been veering increasingly toward biology at Arizona State University in Tempe, who was part of the international team that conducted the magnetic orienteering research I wrote about today. He will be able to add some real rigor to the answers to some of your questions, like, for example, exactly what that equation means over the bird's head in today's graphic!
Devens, I will let you introduce yourself or greet the audience here ...
Devens Gust: Hello - This is Devens Gust, from Arizona State University. I will try to help Rick out with some of the more technical aspects when I can.
washingtonpost.com: Graphic: Flying With a Chemical Compass?
Dublin, Ohio: Do birds actually see (with their eyes) the magnetic field or do they just sense it during migration?
Rick Weiss: The short answer is, nobody knows. Since birds can't talk to us about what they're perceiving. SOme scientists believe it is perceived through the visual system, so would look like something (a dot to follow? A line? A color?) Others think it may be a physical sensation. My idea: can we train a parrot to talk about this stuff with us?!
Herndon, Va.: How do scientists believe shifts in the Earth's magnetic poles affect bird migration? Would this newly discovered element improve a bird's ability to migrate in times of magnetic shift, take away from it, or have no impact at all?
Also, are there signs of changes in bird migration patterns resulting from global warming? For example, birds not going as far south for the winter?
Devens Gust: The mechanism we are studying is sensitive to the direction and magnitude of the magnetic field, but does not distinguish between North and South magnetic poles. Thus a pole reversal would not have any effect once it was over. Of course, if the Earth's field actually went to zero for a while, that would have a major impact.
Barnes Ghaut, Nevis, West Indies: What effect will the eventual collapse and reversal of the Earth's magnetic field have on migratory species? We know it's coming, just not when.
Rick Weiss: Scientists told me that these shifts, although they can happen quickly by geologic time scales, happen slowly enough (over many thousands of years, which is many bird generations) so that evolution could probably keep up and the birds could "learn" as it shifts (ie. the ones that are slightly different enough in their perception to correct for the shift would live and reproduce, while those sticking with the last generation/version of compass bearings would die off).
Angleton/Lake Jackson-Texas : We are on a major flight path for many migratory birds. We average more species than any county in the U.S., and possibly North America. It is legal in Lake Jackson Texas, the home of the Gulf Coast Bird Observatory and many refuges and such, for cats to roam at will. Would you have a message for the city leaders about our birds safety and the importance of birds to our society and the environment. So far,they have not listened.
Rick Weiss: I have mixed feelings about this, as a cat lover and owner and as one with bird feeders (dubbed by cynics as 'cat feeders') in my yard. I know I have read that cats, taken together, take a terrible toll on birds. That said, leashing them seems impractical. And I have to wonder whether far more damage to migratory bird populations is not being done by deforestation in the subtropical areas where these birds go to in winter. Has anyone seen a good cost/benefit study of controlling domestic cats as a means of saving migratory birds?
Lafayette, Ind.: In what ways do we already, or can we in the future, take a lesson from the bird's use of magnetic fields for navigation and incorporate in our own technology advances? What can we learn for our human use?
Devens Gust: The possible mechanisms of bird migration do illustrate one important point that we already make use of, at least when we think about it. There are two aspects to navigation. One is knowing where you are, and the second is knowing which way to go to get to your destination. I have a hand-held navigation device that helps with both things. It has a GPS to tell me where I am, and a magnetic compass to tell me which way North is. Both are necessary. Animals would need similar information, and it is possible that different magnetic mechanisms give the two kinds of information.
Fort Washington, Md.: We are very fortunate to have a migratory route of the "real" Canadian geese over our homes. During the last two weeks of August, it never fails to see hundreds of geese flying over at one time. I call them "real" Canadain geese vs our "resident" geese who fly from golf course to the nearby football and softball fields.
Rick Weiss: It does seem that there is a new species of goose evolving that requires manicured lawns for their survivial, and whose main ecological function seems to be to fertilize those lawns.... and keep people busy washing their sneakers ...
Las Vegas, Nev.: What evidence is there that birds can detect magnetic fields?
Devens Gust: There have been many studies by biologists that show that birds and other animals can detect magnetic fields. Many of these involve exposing the animals to fields that are different from those of the earth, and seeing whether their sense of direction is disturbed. It has also been shown that magnetic direction sensing by birds requires light, and in fact light of certain wavelengths.
Havre de Grace, Md.: My comment is this: Portmann, who was the director of Basle University's Zoological Institute for 25 or so years, gave grounds for not considering magnetic lines of force as the principle guiding agent in bird migration. I translated and published, through Mellen Press, a number of off-prints of Portmann's work; you might read my translation of his THE ORIENTATION AND WORLD-RELATION OF ANIMALS:NEW RESULTS OF BIOLOGICAL RESEARCH in, "Essays in Philosophic Zoology," The Edwin Mellen Press, 1990; pp. 3-20.
Prof. Richard B. Carter (Ret.)
Devens Gust: Thanks for the reference, which sounds interesting. I will check it out. There is plenty of evidence that indicates that birds do in fact use magnetic direction finding. However, they undoubtedly use other clues as well, such as recognizing landmarks, checking the direction of the sun, etc. Which is most important is a tough question to answer, and probably depends on the particular circumstances.
Rick Weiss: Devens, I have a question for you: I wonder if you could briefly describe how someone who starts off in chemistry (the field everyone seems almost proud to say they failed in high school, while they loved biology) got into birds.
Devens Gust: OK, Rick. Every biological function has, ultimately, a chemical basis. Biology is a masterful example of the application of chemistry, and of the related field nanotechnology. As such, biology is a major source of inspiration for some chemists (like me). For example, a major part of our research involves "arificial photosynthesis," which is the application of the chemistry of natural photosynthesis to solar energy conversion. In fact, this bird navigation research grew out of our photosynthesis work.
Munich, Germany: The possibility that magnetic field lines may be plainly visible to birds like the dashed line in the middle of a road, is interesting, but somehow they also have to know that they're supposed to follow those lines, and in the right direction. Maybe Mom gives chicks their driving or flying lessons.
Rick Weiss: You are right that there is a big "black box" when it comes to our understanding of how birds and other animals "know" how to use the magnetic information they are apparently sensitive to. In fact, this has been a confounding element as scientists have conducted experiments to see which parts of the se animals are crucial to the magnetic reception mechanisms. If you do something that disrupts navigation, how do you know if you have disabled the receptor system itself, or disabled somehow their perception of, or proper acting upon, that information once it is recieved? Again, as per a previous question, some of these questions are going to be very difficult to answer until 1) we get a bird to talk about its experience or 2) scientists devise more finely tuned tests of indiviudal elements of the bird's sensory systems to really see how they are doing this.
Devens Gust: Rick is right about that. Studies like ours only address the basic physical and chemical mechanism by which birds could sense magnetic fields. Other studies are necessary to "track" the signal produced by this mechanism through the nervous system and to some part of the bird's brain, and then to understand how the bird uses this information, in combination with other information, to know where it is going, and where it should go.
Falls Church, Va.: Can you suggest any ways for me to use magnets to prevent birds from pooping on my car?
Rick Weiss: Yes: Cover your car completely with magnets.
Whenever a bird poops on your car, remove the soiled magnets and replace them with clean ones.
Let me know how this works. If my hopothesis is correct, we might be able to publish the results in Nature.
DC: How would you design an experiment, or series of expts, to test whether this new mechanism is likely to be operating in real birds?
Rick Weiss: One of the first things you'd want to do -- which some scientists are dojng already -- is just to find a molecule inside the bird's eye, for example, that has the properties of being sensitive to/responsive to magnetic fields of the strength of the Earth's (which by most standards is very weak) and which works at temperatures that birds live in (as opposed to the molecule synthesized in the experiment that I describe today, which is responsive to such weak magnetic fields only at very cold temperatures). That would at least show the plausibililty of a working mechanism in vivo. From there, scientists have suggested to me a few approaches to testing that mechanism's real efficacy. One is to create a genetic "knock out" -- a variant of that bird species that lacks the gene to make that chemical in its body, and see if these birds have trouble navigating. I will let Devens add some thoughts here, too:
Devens Gust: There are two general, and complementary, approaches. The first, outlined by Rick, is to find the system in birds that carries out the function, and then study its structure and function through biophysical structural techniques (X-ray crystallography, NMR spectroscopy, etc.), and through genetic manipulation of the proteins involved. A second way, which we are studying, is to use what we have learned to design better model systems that could function under the conditions of temperature, etc., where the bird operates.
Chester, S.C.: I have a vague memory of some research, that was done around 1980, suggesting that the pineal body played some sort of role in bird migration. Is my memory failing me?
Devens Gust: You are correct. There is evidence that the pineal gland, which is light sensitive, may play some role in magnetic navigation in some animals. There is also excellent evidence that the eyes are involved. It might be that some animals use one, and some the other, or they may use both.
Peaks Island, Maine: Are migratory routes altering due to changes on Earth's surface (not changes of magnetic field)?
Rick Weiss: One of the interesting things about magnetic migration is that, even though the Earth's manetic field lines run basically straight and give birds the option, it seems, of making a bee-line for wherever they are going, birds do not fly that way, in part because they have to find good resting and feeding places along the way. Many birds that use magnetic navigation take very indirect routes, following shorelines and/or moving from wetland to wetland, as suits the requirements of the trip beyond their navigational needs. Some experiments have shown that visual landmarks, as well as solar compass work, all can contribute to a bird's ability to get to where it is going. So as global warming changes icy shorelines, or as development leads to the destruction of wetlands etc, it seems we can expect to see at least some changes in migratory routes.
Falls Church, Va.: Recent research has shown that resident Canada geese ... those born locally ... will migrate north in the spring (early June) in a molt migration if they do not have goslings (failed nesting or juveniles under 3 years old).
Could this be the mechanism they use to find the way even if they have not flown the path before?
Devens Gust: The geese could certainly use magnetic navigation to find their way north. However, this would only be the compass. Something in their brain and other inputs would have to provide the motivation, and let them know when they get to their destination.
Charlottesville, Va.: Have you examined the migratory distances of birds compared to the chemical structures of their beaks and eyes? Would an albatross (or some other long distance migratory species) have more magnetite in its beak than, say, a junco?
Devens Gust: I don't know how much has been done in terms of correlating physiological structures with migratory habits. However, all birds have to navigate to some degree, just to get around their local area. Some people have proposed that birds may have magnetic "maps" that help them get around locally.
Rick Weiss: Another question from me, Devens: Is there any evidence that humans are in any way sensitive to magnetic orientation cues? I know that a few years ago scientists at Brown University discovered a new kind of blue-light receptor in the retina that seems important for daily rhythms and may be connected to pineal activity. Might this be part of a magnetoreception system for us? Do people get disoriented after an MRI?
Devens Gust: I am no expert in this, but I believe that there are some studies that suggest that humans may be able to use magnetic orientation. The jury is still out on that one.
Saratoga Springs, N.Y.: Greetings from your old upstate neighbor! This is not a migration question, but Rick -- I remember a few years ago you wrote about crows disappearing from the DC suburbs and I had noticed the same thing while living in Silver Spring. Has there been any change? Up here, we still have plenty of them around.
Rick Weiss: I have noticed just this year that more crows are back, at least so far. But not tons of them, and I recall a similar uptick last spring, which did not seem to pan out to a big population return. My theory is that once mosquito season kicked in last year (and perhaps again this year) the resident West Nile virus population knocked the crows down again -- and will again this year unless some of those birds have developed resistance. We shall see.
Meanwhile, the helicopters were buzzing us in Takoma Park this morning, spraying "bt" against Gypsy moth caterpillars, so you might see a lot of dead caterpillars around in the next few days, which may or may not be appealing to birds.
Devens Gust: This is a fascinating topic, and I am glad that so many people are interested in it. There is still a lot of research to be done by the scientific community before we know the whole story.
Rick Weiss: Thanks to everyone for logging on and for appreciating The Post's coverage of science. You can't spend ALL your time reading about the election, right? Your science writers are here to remind you that Evidence will take you Rhetoric cannot!
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