Thursday, September 21, 2006

Evolution in Action

Charles Darwin observed the finches of the Galapagos Islands and speculated about how they had developed their traits. Thus he developed his theory of evolution.

Now Princeton biologists, Peter and Rosemary Grant are observing the evolution of those finches.

For years, the Grants had observed finches with various-sized beaks foraging for seeds. The large-beaked birds went for the larger seeds and the small-beaked ones ate the small seeds, but in 2003 and 2004 drought reduced the food supply and the larger-beaked finches began to die off. Another variety of large-beaked finches were eating all the big seeds before the medium ground finches could get them. One year later, the Grants observed that the medium ground finches had smaller beaks which allowed them to compete for smaller seeds. Their evolution was fast and dramatic.

Last year our trees were alive with the activity of chickadees and finches, but this year fewer birds are visting our feeders. The count of wild birds is down throughout the county, but no one knows why. We're seeing a lot of hummingbird activity, so many we had to add another feeder. We have a moderate amount of chickadees this year but hardly any finches.

We had an excess of flies this year, maybe because there were fewer birds to eat them? The year before we had an overabundance of spiders. A neighbor made the observation that watching our cycles, he had an idea about how Chinese astrology began.