Songbirds Not Always Singing a Happy Tune

Cindy Gulledge pulled a vial from the laboratory refrigerator. Sitting at the bottom of the tube of clear liquid was what looked like a gray wad of chewing gum that had just been scraped off the underside of a desk.

It wasn't gum. The gray globule was the brain of a dark-eyed junco, a songbird that visits Alaska spruce forests in the summer. Gulledge, a graduate student at the University of Alaska's Institute of Arctic Biology, knows her way around a junco brain. She studies them to better understand how and why birds sing. Junco brains also give Gulledge and other researchers a simple model that can be used to gain insight on how brains control animal behavior.

Gulledge and Pierre Deviche, an IAB associate professor of animal physiology, said the wonderful songs wafting from Alaska forests are probably all coming from the beaks of male songbirds. Although it sounds as if the boy birds are crooning the joys of being alive, Deviche said songbirds are acting more like street punks than angels.

"It's a territorial song, probably something like This is my little plot. Get out of here! " he said.

The males also sing to attract mates, although much less frequently. And even though many Alaskans wake to a symphony of bird songs in spring, migratory songbirds don't sing throughout the summer in Alaska. Dark-eyed juncos, for example, become conspicuously quiet in August. In late summer, songbirds still communicate with calls (clucks or clicks with fewer syllables than songs), but the songs are stored in their tiny brains until the following spring.

By staining thin slices of junco brain blue and looking at them under magnification, Gulledge has seen that song-related areas of the junco brain grow in the spring and shrink in the fall. The growth of a junco's gray matter devoted to song is triggered by testosterone production, which is spurred by increasing daylight.

A great debate among songbird studiers is whether birds are born with the ability to sing or whether they learn to sing in a process similar to how baby humans learn to talk. Dark-eyed juncos, who fill the woods with a melody that sounds much like the ring of a cordless telephone, need to be taught how to sing, Gulledge said.

Young male juncos hear songs while they are still in the nest. Listening to other male juncos, chicks learn what a junco sounds like, Gulledge said. When they begin their migration north the next year and the testosterone starts flowing, the yearling juncos are able to remember the melody, pitch and rhythm of a junco's song.

As proof that juncos don't have an "innate," or preprogrammed, ability to sing, Gulledge told of an experiment in which juncos were kept in isolation and heard only the songs of white-crown sparrows. As the juncos matured, they sang the songs of white-crown sparrows. Other species of songbird, such as many of the flycatchers, do seem to have an innate ability to sing, but Deviche noted that flycatcher songs are less complex than most songbirds'.

It takes practice for a junco to sound like a junco. Deviche said he's heard robins in Oregon sing funky, off-key tunes while they rehearse their songs in early spring. By the time songbirds reach Alaska they've worked out the kinks; we hear pure tones and predictable melodies.

Those tiny brains do much more than allow songbirds to fill Alaska springtime forests with music. By following the travels of banded juncos on the university campus, Deviche has determined that juncos often return to the same patch of spruce trees, and even perch on the same branch, year after year. The juncos zero in on their favorite spruce even after spending the winter in South Dakota, Missouri, or somewhere else millions of trees away from here. Hmmm. The next time someone calls me bird-brain, I'll take it as a compliment.