The incredible shrinking bird brain

Nature is amazing. The other morning on our local NPR radio station, on a program called Bird Notes, I learned about a sparrow that can sing one day and then not the next. Actually, in the spring, this particular sparrow can sing its little heart out. The idea is to attract a mate. But as the summer ends and the bird has presumably found its partner, a part of its brain shrinks -- the place where the sparrow stores up its songs. The result is that the sparrow cannot remember its tunes. With its smaller brain, the bird is slightly lighter and thus more easily able to escape danger. The next spring when the bird again needs a mate, the section of the brain grows back. If the sparrow were a "thinking bird" it might say to itself, "Oh, now I remember."