The indigo bunting might be the bluest of all blue birds. Except…unlike other cerulean species—for example, blue jays—male indigos don’t actually have any blue pigment. Their plumage is black, but it refracts light, which produces the blue colour that we perceive. So, depending on how sunlight hits them, the birds can actually look black, or even green.
The male indigo sings a lot—into August, later than most other species. He’s loud, and not just in the morning as part of the dawn chorus. Indigo buntings sing through the middle of the day, even deep into the summer. Other species start around an hour before sunrise, then mostly hush up once the day is bright. The sunlight signals that it’s time for them to quietly go about their important business. But indigo bunting don’t care!
Indigo buntings aren’t particularly good singers, but they are dedicated. Young males learn to copy their fathers’ songs; once the first breeding season hits, though, they’ll often try to mimic the song of a dominant, older male. If the youngster’s cover is good enough, it can trick other male indigos into keeping away, and let the new bird establish a big breeding territory. And if the territory is large enough, and there’s abundant food (insects and berries), a male indigo bunting can score two baby mamas in one breeding season. Males that establish only small territories, on the other hand, might sing all summer without finding a mate. Aww. Well, you tried your best, buddy.
Other brightly-coloured species, such as common yellowthroats and red-winged blackbirds, are also polygamous. In the case of an indigo bunting, it’s partially because the female does all the nest building, incubating, and most of the nestling care. Not fair! But probably beneficial. Females are plain looking, but males are striking enough that predators can recognize them, and be drawn to the nest.