Bird Navigation is an amazing, mysterious thing. For years, birds have outsmarted scientists over this issue, mainly I think because people looking into navigation originally made the incorrect assumption that birds are birds and there is a navigational method that they use. However, we now understand that birds vary in how they navigate, and many if not all bird species use multiple approaches to navigation.
So, consider the question that often comes to people’s mind when they realize that the Earth’s magnetic field often changes a great deal in intensity, and in fact, flips around completely now and then: “What happens to the migratory birds when the magnetic field goes upside down?”
The answer to that, at least these days, is that birds are not so dumb.
I suppose it is possible that bird use of the Earth’s magnetic field co-evolved with changes in the magnetic field, so any bird that relied to much on it was selected against, but that is just speculation. Also, consider the possibility that modern birds descended from an animal that migrated by foot, or a form that flew only a little now and then but was mostly terrestrial/arboreal and not aerial. In other words, bird migration, like so many other bird features, may well have emerged in incipient form before birds. (See this and this for more on that sort of thing.)
Also, consider this. Bird migration is cool and important and a major adaptation right? So we might expect that the birds with the best navigational abilities are also those that do the most navigation. But what about pigeons? Homing pigeons are famous navigators, but pigeons are not really migratory. This suggests to me that the abilities that birds incorporate into migratory behavior are at least in part basic day to day getting around abilities. In human terms, your ability to navigate your way from your home in Springfield, USA, to Bora Bora is the same ability that gets you from home to the grocery store and back, slightly adapted for a larger scale.
The story of how this research came about is interesting, and chronicled here. Here, I just want to give you the key results.
There is a lot of electromagnetic noise created by humans, and there has been concern that this energy is harmful. However, extensive research has shown no evidence of harmful effects. Indeed, there are reasons to believe that normal background anthropogenic electromagnetic energy is highly unlikely to cause harm. All this energy can really do is to cook you, like in a microwave, but for that to happen you would need to be in a microwave (or perhaps right next to a very strong emitter, so do avoid climbing those huge towers with the microwave antennas on them!). Your cell phone emits this energy, and it can not harm you.
However, this energy does muck up a bird’s ability to access the Earth’s magnetic field to use in migration. From the abstract of the paper:
… Here we show that migratory birds are unable to use their magnetic compass in the presence of urban electromagnetic noise. When European robins, Erithacus rubecula, were exposed to the background electromagnetic noise present in unscreened wooden huts … they could not orient using their magnetic compass. Their magnetic orientation capabilities reappeared in electrically grounded, aluminium-screened huts, which attenuated electromagnetic noise in the frequency range from 50?kHz to 5?MHz by approximately two orders of magnitude. When the grounding was removed or when broadband electromagnetic noise was deliberately generated inside the screened and grounded huts, the birds again lost their magnetic orientation capabilities. The disruptive effect of radiofrequency electromagnetic fields is not confined to a narrow frequency band and birds tested far from sources of electromagnetic noise required no screening to orient with their magnetic compass. These fully double-blinded tests document a reproducible effect of anthropogenic electromagnetic noise on the behaviour of an intact vertebrate.
So, there you go.
Here is a video from the research team discussing the results:
Greg Laden has been watching birds since they were still dinosaurs, but has remained the consummate amateur. This is probably because he needs better binoculars. Based in the Twin Cities, Minnesota, Greg is a biological anthropologist and Africanist, who writes and teaches about Evolution, especially of humans. He also blogs at Scienceblogs.com. Greg's beat is Bird Evolutionary Biology. One could say that knowing the science of birds can make the birds more interesting. But really, knowing about the birds that go with the science is more likely to make the science more interesting. And thus, birding and Neo Darwinian Theory go hand in hand. Darwin was, after all, a pretty serious birder. Greg has seen a bird eat a monkey in the wild.
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