The Indigo Bunting, cerulean on its body and a brilliant indigo on its head, enjoys brushy early successional habitat throughout Wisconsin. These birds settle into the summer breeding season with the blooming Blephilia, exploding onto the scene with the blue spiderwort. Blue is a rare color in the matrix of communities and animals calling southern Wisconsin home. Bellflower, spiderwort, bottle gentian, and the alien roadside chicory are some of the few plants with blue blooms.
But the indigo is not truly blue. The bird does not have blue pigment, but rather refracts blue light. If you hold a bunting feather facing the sun, you will see, the dull brown color of melanin. If instead the sun comes from behind the feather, microscopic structures will refract that unmistakable cerulean back toward you.
Indigo Buntings use stars as more than just plumage enhancement. Besides refracting the sun's rays, the birds also use the stars to orient themselves during migration. The behavior is learned, as a sort of map from other buntings. Researchers discovered this by studying Indigo Buntings in a planetarium versus a natural setting under the night sky.
Another extraordinary feature of the bird is that they have worked around brown-headed cowbird nest parasitism. Indigo Buntings will abandon their nest if cowbirds parasitize it, or they will build over the cowbird egg. They will readily re-nest and will sometimes nest late enough to avoid the cowbird breeding season and thus avoid parasitism.
Indigo Buntings and their young have been making their distinctive call ("fire, fire, where where here here") along Prairie Lane and throughout the sanctuary. Impressive numbers of buntings sing along woodland edges early each morning, waking me with their warning of fire.
By Drew Harry, Faville Grove Sanctuary land steward