The brown-headed cowbird may parasitize this species. Indigo buntings abandon their nest if a cowbird egg appears before they lay any of their own eggs, but accept the egg after that point. Pairs with parasitized nests have less reproductive success. The bunting chicks hatch, but have lower survival rates as they must compete with the cowbird chick for food.
This is a migratory bird, with nesting grounds across most of the southern half of the United States and much of northern Mexico, migrating south to Central America and in very small numbers to northern South America; the southernmost record comes from eastern Ecuador. It eats mostly insects, but it will also eat snails, spiders, seeds, grains, and wild fruits. The blue grosbeak forages on the ground and in shrubs and trees.