Laura Erickson's For the Birds

Indigo Buntings

(Recording of an Indigo Bunting)

Last week I heard from an alert Duluthian, Eileen Bonifaci, who was pleased to discover an Indigo Bunting in her Hunter’s Park yard. Indigo Buntings are fairly common breeders in open areas of the Northland, but not many people notice them. Even though males are bright blue and sing on conspicuous perches, without good lighting they often appear black or gray–it’s when the sun hits them just right that their extraordinary color catches the eye.

Blue feathers are not colored by pigments, unlike feathers of other colors. If you put an oriole feather in a blender and ground it up, you’d end up with orange mush, and if you ground up a goldfinch’s feather you’d end up with yellow, because those colors are caused by pigments; but if you ground up a blue feather from a jay, a bluebird, or a male Indigo Bunting, you’d end up with gray mush. The color blue in feathers is a structural color–the feather cells are arranged in a precise way so that only blue wavelengths of light are reflected. If the cells are rearranged, the color is lost. Female Indigo Buntings are dull brown, with faint streaks.

Indigo Buntings are probably not genuinely North American birds. They spend about seven months of the year in Central America, and only come up to the Northland during the breeding season, perhaps believing that Noriega’s Panama is no place to raise babies. The female weaves the cup-shaped nest from grasses, snake skins, strips of bark, and anything else handy, from feathers and hair to facial tissues. The nest is usually only a few feet from the ground in a tangle of shrubs or a raspberry patch, but occasionally she builds it 5-15 feet up in a tree, just to confuse ornithologists.

While she’s at work building the nest and incubating the eggs, the male spends his time singing to declare his territorial boundaries. The song is a long string of paired notes—each pair on a different pitch. One description of the song is “sweet- sweet, where-where, here-here, see it-see it.” Unlike most birds, Indigo Buntings sing any time of day, from sunrise to sunset, and often sing as late as August, after other birds have packed up their instruments for the season.

Besides singing, the male brings food to the female on the nest, and then helps feed the babies. Raising baby Indigo Buntings is a quick process—it takes only 12-13 days to incubate the bluish-white eggs, and the babies are ready to fly when they’re only 8-10 days old. Each pair rears two broods a year.

Back in 1945, when the whole world was temporarily insane, an ornithologist designed an experiment to see whether male birds really serve an important function in child-rearing: he found a pair of nesting Indigo Buntings and shot and removed the male. By the next day the female had obtained a new mate, and the scientist shot him, too. Each day another male Indigo Bunting came to the aid of the female, and each day he was shot, until the scientist had removed nine males. He finally left the tenth male undisturbed to help the female raise her babies. Fortunately, native American birds are now protected by law, and scientists need a better reason than that to kill them today.

Even though ornithologists allow them to nest in peace now, Indigo Buntings have other problems. They’re killed in huge numbers during migration in collisions with tall buildings and radio and TV towers, and the ones that make it home to the tropics have to deal with dwindling habitat as the destruction of the rain forest continues. Every Indigo Bunting in the world is actually a tiny survivor with a feisty, if tenuous, grip on life, and attention must be paid.

(Recording of a Indigo Bunting)

This is Laura Erickson, and this program has been “For the Birds.”