Slideshow: Backyard birds photographed through windows

Indigo Buntings are sexually dimorphic, and males in the summer are a brilliant blue. Like all “blue” birds, Indigo Buntings do not have blue pigment. Whatever appears blue on any bird (bluebirds, Blue Jays, and others) is the result of refracted light, created by microscopic air bubbles in the feathers. The precise arrangements of these air bubbles in nanostructures scatters a narrow range of wavelengths of light, like a specialized prism. As a result, male Indigo Buntings appear blue even though they are actually a dark brownish black.

In contrast to blue males, females are almost entirely a plain light brown. Also, in contrast to males, females do not sing. Males have complex songs for courtship and to defend their territory. Although males are usually monogamous, they typically do not help in incubating eggs or raising chicks.

Indigo Buntings migrate about 1,200 miles and spend their winters in Central America and the Caribbean. They migrate at night, guided by the stars, able to adjust their flight accordingly for the continuously changing orientation of night skies. In their winter habitats, male Indigo Buntings have brown plumage and look like females.

The birds have an average lifespan of approximately 9 years. The oldest one documented in the wild was a male banded in Ohio in 2001; at the time of his recapture and rerelease, also in Ohio, he was at least 13 years and 3 months old.