Why Birders Love the Blues - It's no coincidence that the indigo bunting has been the focus of a number of landmark bird behavior studies - description and behaviour of bird

Oh my, the song of the indigo bunting, the bluest of all our blue birds. As sweet and variable as a lick from Benny Goodman's clarinet, it swirls from dawn to dusk, from May to September, over the thickets and overgrown pastures of eastern North America. There, this little finch settles in to raise a brood or two before returning to tropical climes.

Struggling for words, field guide authors variously describe the male indigo bunting's aria as "lively, high and strident," "a rapid, excited warble" or, more prosaically, "a series of varied high-pitched phrases, usually paired." The bird encyclopedist John K. Terres interpreted it as "sweet-sweet, where-where, here-here, see-it, see-it."

Edward Howe Forbush, a famous New England ornithologist in the early twentieth century, effused: "The male seems to delight in singing during the hottest part of the summer days, when other birds are resting in the shade. He will sing his way from the bottom of a tree to the top, going up branch by branch until he has reached the topmost spire, and there, fully exposed to the blazing sun, he will sing and sing and sing."

Indeed! A male indigo bunting will utter as many as 680 songs an hour if he's looking for a mate. That's one amazing fact gleaned from an impressive number of scientific papers that focused specifically on the species' song. Another: A young male settling on a breeding territory for the first time doesn't sing his father's song, like most songbirds; instead, he copies his new neighbors.

Few birds, in fact, have had their songs scrutinized as thoroughly as this abundant, popular Neotropical migrant, always a showstopper for birders on midsummer field trips. But the indigo bunting was also the star of a landmark experiment showing that young birds learn the constellations in the northern sky in order to orient themselves on their first night flight to southern wintering places. Then there were studies of indigo bunting breeding behavior and genetics; the results suggested that infidelity might be widespread among avifauna long assumed to be faithfully monogamous.

The species at the center of these investigations is one of four colorful finches that inhabit brushy and weedy places between the borderlands of Canada and Mexico. These birds comprise a small genus (Passerina) in a huge and widespread family of seed-eating songbirds. Gaudiest of the quartet is the painted bunting, a favorite backyard feeder bird in the Sunbelt states. The lazuli bunting, blue with a cinnamon breast, is the indigo's counterpart in the West and the two hybridize where their ranges overlap. The varied bunting, a multihued but secretive resident of desert washes in the Southwest and northern Mexico, completes the group.

The bird books also have trouble conveying the color of a male indigo bunting in full nuptial plumage. Is it "rich deep blue" or "brilliant turquoise blue" or perhaps "cobalt with a purplish cast"? It depends in large part on the light. As the ornithologist John Farrand, Jr. explained, "Indigo buntings have no pigment; they are actually black, but the diffraction of light through the structure of the feathers makes them appear blue." (In winter, the male loses much of his blue sheen and looks more like the plain brown female.)

The species is remarkably common east of the Great Plains wherever there are abandoned fields, old burns, shrubby swamps, forest edge, cutover lands, utility rights-of-way, unmowed roadsides and little-used railroad grades. Estimates of the species' continental population, based on numbers from the annual Breeding Bird Survey, range as high as 40 million breeding pairs. The highest counts come from Kentucky and Tennessee, where the indigo bunting may be the most abundant songbird.

Yet as Cornell University ecologist Stephen Emlen notes, many birders are unaware they have indigo buntings in their neighborhoods. "I've turned people on to a very exciting bird in 30 seconds by pointing out the paired note structure of its song," says Emlen, author of the research on migration orientation in the late 1960s.

A lay observer could easily conclude that male indigo buntings are such vigorous songsters because they have relatively little else to do from the day they arrive at their breeding territories-two weeks ahead of the females-until their progeny have fledged. It is the female that spends more than a week building the open-cup nest, which is woven into a shrub 2 or 3 feet from the ground. It is the female that incubates the three or four eggs and mobs predators near the nest. And it is the female that crams insects and spiders into the throats of the hungry nestlings.

The male may finally enter the picture a few days after the young birds leave the nest, taking over their custody so his mate can start another brood. "Such relief from caring for fledged young may be the male's main direct contribution to the breeding success of the female in his territory," relates Robert B. Payne, curator of birds at the University of Michigan Museum of Zoology who has led studies of buntings since 1978.