Birds are Growing Smaller as the Climate Grows Warmer
Posted by Kelly Smith on Tue, Mar 23, 2010
Scientists have been telling people for years that global warming causes problems for animal populations. Migratory birds such as Europe's pied flycatcher are a prime example of the known negative effect of climate change on animals.
As the climate grows warmer, the caterpillars that ordinarily serve as a food source for baby flycatchers may emerge earlier in the spring than the usual arrival of the flycatchers from Africa. The birds cannot easily change their migration pattern, so many starve.
Now scientists have made another startling discovery about the effect of global warming on migratory birds. North American songbirds have been growing smaller over the last fifty years as the climate has grown warmer. This discovery falls in line with biology's Bergmann's Rule, which states that animals in warmer climates tend to be smaller.
North American birds that spend the winter in the tropics seem to be most susceptible to this effect. The scarlet tanager, for example, has decreased in mass by 2.3% over the course of about twenty generations.
The consequences of these changes are uncertain. Dr. Josh Van Buskirk, a professor at the University of Zurich, Switzerland, does not see that this change in weight and wing span in birds is harmful in any way, as population sizes seem to be remaining largely constant.
Such studies continue, as birds provide a glimpse into the effects of global climate change. The National Audubon Society tells us, "When it comes to global warming, birds are like canaries in the coal mine, showing us that temperature increases are reshaping our ecology in potentially dangerous ways."
Photo via Eric Begin