The research paper for today (published May 2009 in Nature) looks at zebra finches, a type of songbird. The song of zebra finches is like a cultural trait: individual finches have small variations in their song and geographically separated finch groups have local song dialects. Overall, though, the song from the zebra finch in the wild (called the “wildtype song”) can be recognized and described. Songbirds learn to sing during their development by being exposed to adult singing males (females lack a singing ability, but at Zebra Finch Idol, they do the judging). This begs the question: What if baby zebra finches aren’t exposed to singing males? To investigate this question, the group of researchers from New York took zebra finch eggs and raised them individually in sound-proof rooms.
Now a Pop Quiz for my readers, for 20 brownie points:
What happens when baby zebra finches aren’t exposed to adult singing males?
A) They never sing.
B) They sing normally.
C) They sing poorly.
D) They spontaneously break out in “A boy named Sue”.
Think about it: if the song is encoded in their genetic code, then it shouldn’t matter whether they are exposed to it or not, and the answer would be B. If the song isn’t encoded in their genetics and they only learn to sing by imitating adult birds, then the answer would be A. D was a red herring, and the correct answer is actually C. The isolated zebra finches sang, but the sound didn’t really resemble the wildtype song.
Good science is all about asking the right questions. Instead of stopping there and analyzing what went wrong, the researchers thought of a really creative way to address the results. They took a second batch of zebra finch eggs (the second generation), and raised them again individually in a sound proof roof, but this time each baby was raised with one adult bird (a singing tutor) from the first generation (the ones who sang poorly). I’ll spare you the quiz this time: the birds from the second generation learned to sing just like their tutors, poorly. However, their song was slightly different. The rhythm and other characteristics of the second generation song were a little closer to the wildtype song. And so the researchers continued: a third generation of birds was raised, this time with second generation tutors. And believe it or not, each generation sang a little more like the wildtype birds and by generation 4, the song was very similar to the original wildtype song.
The conclusion from the article is that song culture is partly encoded in the genetic profile of a population and partly encoded in the environmental variables. Song culture is also a “multigenerational” phenomenon, because it takes a few generations to emerge. It is a bit disappointing that this study doesn’t also look at the mechanisms of what’s happening. For example, song development is known to be associated with something called neurogenesis, which essentially means the birth of new brain cells. Could it be that over a few generations, there is an orderly progression of connections between the new cells? Are the brain cells and associations between brain cells getting reorganized with each new generation? The researchers do promise to look into it, so I’ll stay tuned and keep you posted.
This is what a zebra finch looks like. Pretty cute, huh?
Reference: De novo establishment of wild-type song culture in the zebra finch. Feher O., Wang H., Saar S., Mitra P.P., Tchernichovski O. Nature 2009 May 3 EPub ahead of print.