Flight of Fancy

Ah, the signs of fall. Trees change their coats, hideous noises emanate from our clocks at obscene hours of the morning, and in the skies great Vs of birds wing their way to more favorable climes. The last of which poses a question: sure, we’d all rather be someplace a little less arctic than New England come winter, but why come back in the summer? Flying such long distances must consume a large amount of energy, so why bother? A September 11, 2006 article (free subscription required) in the Washington Post describes how one group of scientists is attempting to answer that question.

The first question when studying bird migratory patterns is, of course, where do the birds go, and from whence do they come? A deceptively simple question, but how does one actually track a bird? One couldn’t, at least until recently that is. With the constant advance of technology, radio transmitters have continued to get smaller, and now there are examples small enough to be strapped to a bird and not greatly inhibit their flight. Scientists Adrian H. Farmer and Bridget Olson of the U.S. Geological Survey and the U.S. Fish and Wildlife Service respectively have been using this method to study the migratory patterns of the marbled godwit, a species of small shorebird that has been disappearing from some of its historic territory. Their data shows that these birds’ migrations are extensive, covering the territory from Baja California to Alberta Canada. Also, importantly, the study showed that protected areas were used by the birds as stopping points along the way, demonstrating the importance of such land.

The second question: why do the birds migrate? The answer is, well, no one knows. Theories have been forwarded suggesting that the migrations may have started as small journeys to nearby locales where feeding might have been better during certain seasons, and then gradually expanded as following generations of birds found favorable conditions further and further away. A logical explanation, but the only way to find out for certain is for people like Farmer and Olson to do the science.

The work also has current ramifications. Many species of migratory birds, including the marbled godwit, are disappearing. These bird species are possibly more susceptible to human incursions because they rely on more than one area’s condition. If a population of birds summers in one area, winters in another, and stops at places in between during migration, then disruption of the habitat in any of those three locations can threaten the viability of the population. This is why it is important to understand where these birds go so that we can ensure that the destinations are still habitable.

Posted by RWS (2)

Updated on 9/18/06

Just thought I’d add some things in response to the uhh…responses this has gotten. Firstly, I didn’t actually have any information regarding loss of migratory stopover habitat apart from what the article itself mentions and my own extrapolation of the long-term meaning of such loss, which is why I didn’t have a link to something specific there. It seemed to me that this was the greatest immediately actionable aspect of the research, which is why I expanded it more. That said, these people are the conservation group specifically mentioned in the article and seem to be a good demonstration of the kind of multinational commitment required due to the length of these birds’ migrations. As for theories regarding why they migrate, I’ve heard a few, but none that feel particularly definite. A few have to do with physical space, simply put there is less land mass near the equator so the birds migrate north in order to have more space to lay their eggs and forage for food. Another related theory that helps explain the seasonal return is that all birds originated in the tropics and began migrating for the same restricted landmass reason as above. I can see some logic in these ideas. A huge number of birds migrate to tropical regions in the winter; the concentration of birds and therefore competition for resources in these areas must be incredibly high at these times, perhaps high enough to make the energy expenditure of migration worthwhile.

Posted By RWS