All across the continent, no species of songbird is more singular in its song than the little black-capped chickadee (Poecile atricapillus). From the Atlantic to the Pacific, he sings the same tune, like a record stuck on replay: Fee-bee. Fee-bee-ee. Most other songbirds, like people, have developed dialects, so you can tell right off which guy is from Boston or Minnesota or Mississippi. But female black-caps, for whatever reason, have selected males that stick to the mainstream – they like their menfolk cute but conventional – and this has imposed upon the males a prime sexual directive to sing the same way from one end of the country to the other. (If they want to get lucky, that is.)

Which is why it came as a great surprise to the nonbirding public a few years back when it learned the Vineyard’s black-capped chickadees had slipped the musical rut.

The Island chickadee looks just like a chickadee you’d see anyplace else – a gray and white bundle of feathers and energy, less than five inches high and weighing half an ounce, sporting a black crown and a black throat. But the tune that the Island chickadee whistles is unlike the unwavering song you’d hear anywhere else on the mainland. “It’s a source of pride on the Vineyard that our chickadees are unique,” says Matt Pelikan, the Island’s program manager for The Nature Conservancy. “It’s not something that the general population knows about, so we get a kick out of pointing it out to them in the field. The call notes are noticeably different. It’s really weird.”

William Brewster observed the chickadee’s peculiar Island song as early as 1891. Aaron Bagg described it in the Massachusetts Audubon magazine in 1958. And the late Dolly Minis, a longtime summer resident of Chilmark, recorded Vineyard chickadees beginning in the 1970s for the Library of Natural Sounds at Cornell University. (All told, Minis would supply the library with 400 recordings of 227 bird species, working in the field until just a couple of years before her death last summer at the age of ninety-two.)

In the mid-1990s, Minis was part of a team of ornithologists that made an all-out effort to map the strange variation in the song of the Vineyard chickadee. The recording crew was led by world-renowned bird-song expert Donald Kroodsma, whose full-time job, as professor emeritus of biology for the University of Massachusetts at Amherst, is listening to the birds.

At the least provocation, Kroodsma will jump from his desk and run outside to catch the lusty flourish of a hermit thrush. “Once you start listening to birdsong, you can’t turn it off,” he says. “It’s sort of like being in a room full of people with lots of juicy gossip going on. Do you want to turn off your ears, or listen in on what the cardinal and titmouse are saying? Are they hooking up or avoiding matches?”

A tall man kept fit by three decades of tracking birds to remote outposts with a pack of recording equipment on his back, Kroodsma is as dedicated as a Grateful Dead fan. He has spent many a predawn hour road-tripping to wherever the avian-concert tour takes him – by canoe into cattail swamps, by bike down rocky back roads, by ladder to country rooftops.

When he gets home with his recordings, the thrill continues. Using a sonograph, he can see on paper what he’s been hearing indistinctly in the woods. The graph shows time on the horizontal axis and frequency in hertz on the vertical, so that the songs play out on the page in dark etches that look like spiked mountains (the field sparrow’s dawn song), or fuzzy, grassy plains (the wail of the common loon). To Kroodsma, they’re works of art, and the art of listening is seeing. “It’s with my eyes that I hear,” he says.

Sonograph technology has allowed Kroodsma and others to decode an enormous amount about the lives of birds. (Kroodsma got noted in Ripley’s Believe It Or Not!, for instance, for finding that the brown thrasher has 2,400 distinctly different songs.) Once you study bird song on the page, you go into the woods with a new way of hearing. You see a bright red cardinal with its beak wide open and suddenly his call looks like a Morse code of feathery, spiked slashes.

The fee-bee-ee of the mainland chickadee is a fat black hyphen (fee) followed by a lower split line (bee-ee), revealing a whispered break we might otherwise miss. The lines represent the two half-second whistles of the continental chickadee, with the second whistle dropping to a slightly lower pitch than the first. He repeats this two-tone song over and over on the same frequency, until eventually he shifts to a higher or lower range. In his hour or so of singing at dawn, he’ll vary the fee-bee-ee song over a range of frequencies.     

“It’s like name that tune,” says Gus Ben David, director of the Felix Neck Wildlife Sanctuary in Edgartown. “A good birder, like a musician, can recognize the minutest difference by note.” Matt Pelikan, for one, identifies 80 to 85 percent of birds by song. “You have to understand that for some birders, vocalizations are really important,” says Pelikan. “Bird social life takes part largely in the form of sound versus other contact. From a bird’s perspective what you sound like identifies you as familiar, and indicates how you’re going to act.”

To further disentangle the complex symphony of whistles, birders often attach mnemonic words to songs. While Peterson’s Field Guide spells the black-capped chickadee’s song as fee-bee-ee, some birders hear him say ham-burg-er or spring-is-here. The words, like the fee-bee-ee mnemonic, are a loose translation of how the whistles break down into syllables and duration (they do not represent the exact notes, like the vocal diatonic scale of do-re-me). Kroodsma prefers the translation of hey-sweetie. Besides the poetic fact that the song lures females, the hey-sweetie mnemonic makes it easier than
fee-bee-ee to make distinctions when the traditional chickadee song starts doing the twist – as it does on the Vineyard.

When Kroodsma first heard the Dolly Minis recordings of chickadees at the Library of Natural Sounds, he was amazed. Instead of the usual two-tone, pitch-shifting hey-sweetie of the mainland, he heard Gay Head chickadees singing sweetie-hey. Not only was the song reversed, but it was a monotone, sung only at a high and low pitch, omitting the intermediate range. “Wow,” he thought. “They really are different.” He would learn that this was only the beginning.

In May 1994, he set out on a bike across the Vineyard to hear and record the strange song for himself. On his way between Gay Head (now Aquinnah) and Edgartown, he was stopped by a police officer concerned about the shotgun-shaped equipment strapped over his shoulder. (It was his microphone.) Soon he was hearing and adding many variations to the Island song. What the mike picked up “blew me away,” says Kroodsma. “I kept biking thinking, what’s next?”

He began to mistrust his ears. He knew the birds he was hearing were chickadees – they couldn’t be anything else – but this basic, backwards monotone (sweetie-hey) was a mystery. How could the chickadee maintain its two-tone song so consistently for so long all across North America, and then change in all the ways he was beginning to hear on the Vineyard? “What goes on in the mind of a chickadee?” asks Kroodsma. “It’s an alien being trying to tell us something, but I’m not sure what.”

He returned with reinforcements. In May of 1995, beginning at 4:30 each morning, Kroodsma and a team of nine birders stalked the Vineyard woods, looking and listening for more clues. At West Chop, Gay Head, Felix Neck, Chappaquiddick, Edgartown, Menemsha Hills, Vineyard Haven, the Manuel F. Correllus State Forest, and other nature preserves, they captured the chickadees’ songs on tape and put the sounds through a spectrum analyzer. Four days and some 200 recordings later, they plotted their findings on a map of the Vineyard. The following spring, they added about 250 more samples. In 1999 Kroodsma published the findings in The Auk, the journal of the American Ornithologists’ Union.

What they found was that on this small island, only twenty-five miles wide, there were more distinct dialects than on the whole of the North American continent. Perhaps even more surprisingly, apart from a few birds on Chappy, not one of the Vineyard chickadees sang like those on the mainland.
The breakdown goes something like this: At Aquinnah and on much of the western end of the Island, the chickadees sing the backwards monotone (sweetie-hey) at low and high pitch only. Mid-Island they throw in a single tone sweetie-sweetie on high with the sweetie-hey down low. On the Island’s eastern end, the dialect includes a low one-tone sweetie-sweetie and a high sosweetie-sweetie. Only the chickadees from Edgartown let loose on a high and low sosweetie-sweetie.

On Chappaquiddick, the song is even more variable. Across this tiniest of neighborhoods, the fellows whistle their own single version (a monotonal hey-sweetie, sweetie-sweetie, or sosweetie-sweetie), refusing to mimic the songs of Edgartown, right across the harbor. A few Chappy chickadees also sing the two-tone hey-sweetie like that on the mainland (and, again, unlike any other Vineyard chickadee). But the real originals are the Chappaquiddick chickadees that whistle not just one song each, but a repertoire of four. If the Vineyard ever needed a mascot to represent its disconnectedness from mainland uniformity, there the little half-ounce is: the nonconformist chickadee in all his glory.

“I realized that our chickadees were not alike – the Edgartown ones sound so different from the Chilmark chickadees, for instance,” says Pelikan. “But I’m not sure I would have pieced all the regional differences together before Kroodsma’s study.” The study helped map the where of the dialects, but fell short, Kroodsma concedes, when it came to the why of them. Birders can only speculate on that. Our isolation from mainland wildlife surely plays an important part.

Mainland chickadees tend to migrate over the land, trying to avoid the water as much as they can. The occasional chickadee who loses his way and ends up on the Island must either learn the Island dialect or die out. Vineyard chickadees, for the most part, stay put. The four-mile flight back over Vineyard Sound to Nobska Point in Falmouth looks like an insurmountable gulf. “This is nothing, as the bird flies, and some birds, most notably American crows, spend the day on the mainland and return to spend the night, roosting on the Vineyard,” wrote E. Vernon Laux in the Vineyard Gazette. “Yet for a small woodland-loving bird like a black-capped chickadee or a tufted titmouse, this distance over open water might well seem like the entire Pacific Ocean.” A few chickadees land here during the spring and fall migrations, and, for the most part, decide to stay put. Isolation creates a sort of Galapagos effect; unusual characteristics, such as a variation in song, work their way to the fore.

“They don’t look over and say, ‘Geez, I want to fly to Falmouth today,’ ” says Gus Ben David. “So inbreeding is a factor, to some degree, that affects behavior and voice difference.” But genetic testing suggests that the Island chickadee has not evolved into its own species, or even its own subspecies, yet.
Nor is their song encoded in their DNA, as with many songbirds. To verify this, Kroodsma raised black-capped chickadees in the lab and piped in songs for them to learn. He found that the young males ignored the recordings, learning their song from nearby males instead. The birds in each room of the lab sang their own songs, with no particular emphasis on the hey-sweetie norm in nature. Given their ability to sing so many songs, the oddity is that across almost the whole of the continent, the chickadee sings only one.

“If you think of ten of your friends in the same room,” says Kroodsma, “with one transmitting a brief story to the next one, that story will have been modified in some hilarious ways by the time it gets to the last one. Now consider what happens over ten generations, over a vast geographic range. The norm for songbirds is for a dialect to change from one area to another. For a learned song to be so stereotypical is unusual.” The mainlanders apparently have evolved in favor of a pan-continental uniformity.

Kroodsma speculates that Vineyard chickadees developed distinctive dialects back when the Island was largely cleared of trees by European settlers, leaving isolated pockets of chickadee habitat. After reforestation, the dialects came into closer competition across the Vineyard, but must have been ingrained enough to remain so audibly distinct.

The phenomenon does crop up here and there on the mainland, it turns out. Before he heard the Vineyard chickadees, Kroodsma knew of isolated populations with their own dialects in Oregon and Washington, west of the Cascades. Another group of chickadees with their own accent was recently discovered in Fort Collins, Colorado. “When you publish a paper that says their song doesn’t change from the Atlantic to the Pacific coasts, people start listening for the exception to prove you wrong,” says Kroodsma. This cheers him, he says, and he urges people to start listening more closely to find out if they hear new variations where they live.

“On the grand scale of world events, this is probably pretty small stuff,” says Kroodsma. “But it gave me lots of personal satisfaction. What’s intriguing to me and my friends is that while there’s still a bit of a mystery, it’s another link in knowing how the pieces of this singing continent fit together.” He looks forward to the day when he’ll return to the Island to find out if the Vineyard variations have held up in our captive chickadee population. “For what better thing is there to do than to go out to the Vineyard and ride around on your bike listening to the birds?” Kroodsma asks. “All in the line of work, of course.”

The Singing Life of Birds: The Art and Science of Listening to Birdsong, by Donald Kroodsma (Houghton Mifflin Company, 482 pages) was published in April. The book comes with a CD and printed sonograms. The price is $28.