Election Section

Mimicry and Practice to Get the Bird Song Right By JOE EATON

Special to the Planet
Tuesday April 05, 2005

Earlier this year, PBS ran (in its usual annoying fashion, all three episodes back to back) a documentary about American English, with Robert MacNeill traveling around the country and reporting on the state of the language. It was in part an elegy for dy ing dialects (Southern Appalachian, Gullah) and in part a forecast of linguistic change (the Northern Cities Vowel Shift, the lingo of rappers, skateboarders, text-messagers). 

Americans aren’t unique in having dialects, of course—I learned that hitchhiki ng around Britain years ago, and having mutually unintelligible conversations with Scots, Welsh, Yorkshiremen, and Londoners. Nor are humans. The existence of local song dialects in birds has been documented for quite a while. Much of what we know about t he phenomenon comes from the work of Luis Baptista, who was curator of birds and mammals at the California Academy of Sciences until his untimely death in 2002. 

I only met Baptista once, at one of the Academy’s open house nights when members get to go be hind the scenes, meet the scientists, and smell the formaldehyde. But he must have been a remarkable individual. He had emigrated from Macau in 1961 to study at the University of San Francisco and UC Berkeley, and it was at Berkeley that he discovered his key research subject, the white-crowned sparrow. More than half his 120-odd technical publications dealt with the sparrow and its song dialects.  

He had an amazing ear for birdsong. “Luis could stand in [Golden Gate Park], hear a call, and declare that ‘the white-crown had a Canadian father and a California mother.’” a colleague remembered. “It has half an Alberta accent and half a Monterey accent. The parents probably met at the Tioga Pass near Yosemite.” Baptista’s love of music—he was an early fan of Astor Piazzolla—meshed seamlessly with his research interests; his last project was a study of the biology of music and its relationship to bird song.  

Baptista (and other researchers like Donald Kroodsma) found that white-crowns have to learn their loc al version of the species’ song. Their “song tutors” are either their own fathers or males holding neighboring territories. Biologists believe that like other songbirds, they’re born with a built-in auditory template, a generalized sketch of what their so ng should sound like. But there’s a critical period, from 10 to 50 days after hatching, during which they need to hear an appropriate model in order to get it right. White-crowns reared in isolation or exposed only to the songs of other species never prod uce a normal song. In the wild, they begin practicing at about 5 months of age, playing with variations but eventually settling down to the version they heard from Dad. 

It turns out that dialects can be highly localized, with audible differences in sparrow populations only a few yards apart in the same patch of habitat. Males with territories on a dialect boundary can be bilingual. Getting the song right makes a big difference in their social lives, since females are more responsive to the local dialect. And genetic differences seem to mirror song differences. Since song “inheritance” seems to be patrilineal, I have to wonder about Baptista’s bird with the half-Monterey/half-Alberta accent; maybe he was just pulling his colleague’s leg. 

I thought of Luis Baptista and his white-crowned sparrows when I heard a National Public Radio report on some new research by Gary Rose at the University of Utah at Salt Lake City, and later tracked down the report in Nature. Rose and his colleagues set out to study the mechanics of song learning. They knew that sparrows that had been exposed to only isolated phrases of their species’ song were unable to produce a normal song. But when they broke the song into pairs of phrases (AB, BC, CD, DE), they found that sparrows exposed to the sequence of pairs were able to put them together in the right order. And if the sequence was reversed (e.g., BA, CB, DC, ED), the sparrows assembled a “backwards” version of the song (EDCBA), which, as played on NPR, sounded decidedly odd. 

How does this all work in the sparrow’s brain? Earlier research had identified specialized cell groups in the forebrains of songbirds that were associated with song learning and production—the “song system.” Neurons in the song system light up when a bird hears its own song played back. And there is a stronger response to paired song phrases in the correct order than to phrases in isolation. 

It’s not clear at this point whether the neural pathways are laid down when the bird first hears a “song tutor,” o r when it practices its own song during the developmental period.  

Donald Kroodsma’s research on Bewick’s wrens in Oregon suggests that the song tutor may be a neighbor rather than a parent. After leaving the nest, a young male wren abandons his father’s song and picks up the prevailing dialect surrounding his new territory.  

All this has interesting implications beyond the world of sparrows and wrens. There may be commonalities between the neural architecture of learning in songbirds and in humans. And without getting too Chomskyan, we may have our own innate templates for language. Maybe someday I’ll be able to explain, on a scientific basic, how I got out of Arkansas without acquiring an accent, except for that tendency to pronounce “greasy” with a Z, and “Baptist” with two B’s.PA