Bird Brains and Singing

Program Description

Song repertoires vary hugely. While a typical songbird may sing a dozen different themes, some sing just one or two and some have truly enormous repertoires. And even within species, repertoires vary.

Just what determines the size of a repertoire isn't altogether clear. One factor seems to be how many different species songs a singer hears, so good health and a long life can give birds more time and energy to add to repertoires. But local customs can vary, too. Marsh wrens in the eastern US, for example, tend to sing 40 to 60 different songs. That's impressive, but California marsh wrens may sing two or three times that many.

Why? Well, it turns out that the two song control centers in western marsh wren brains (those are areas involved in both hearing and producing songs) are about 1/3 larger than in their eastern counterparts.

So, which came first, the custom or the brain? The classic story would say: well, if singing more songs makes a male marsh wren more attractive to females, then there could be selective pressure over generations that could result in bigger brain centers for singing more songs. But it turns out that the song control centers in the brain can grow during the mating season, when birds are learning songs and singing more, and shrink in the off-season. Even more remarkable is that new neurons can grow in these centers in adult brains, something once thought impossible. So the act of singing itself may somehow spur brain growth.

The growth of new neurons in adult brains has now been found in many species, including us humans, but it was the study of bird brains that first raised this possibility.

Program & Recording Notes

Chris Tenney recorded the marsh wrens near Salinas.