Adult male indigo buntings are brilliant blue during the breeding season, with a darker almost purple crown. Females and young are brown with buff wingbars. They have only a tinge of blue on their tail and shoulders. Indigo buntings are small birds, from 11.5 cm to13 cm long. They weigh 12 to 18 g. They have short, conical beaks and their legs and feet are black or gray. (Payne 1992, Robbins, Bruun and Zim 1983)
Indigo buntings (Passerina cyanea) breed throughout eastern North America from the Great Plains eastward, south of the coniferous forest region. There are also some breeding populations in the western United States, including Utah, Arizona and California. Indigo buntings winter in the coastal regions of Mexico, Central America, northern South America and the Caribbean.
Indigo buntings breed in brushy and weedy areas at the edge of openings. For example, the like the brush along the edges of farm fields, or along rivers, roads or railroad tracks. They also like to breed in weedy open areas, such as old farm fields, or in swamps. In the winter, indigo buntings choose open habitats, such as weedy fields, citrus orchards, savannas, and young forests (Payne 1992).
Indigo buntings are monogamous. This means that one male usually mates with one female. However, about 15% of males have more than one mate. Also, pairs do not stay together for very long. After the eggs are laid, the male leaves the female and she raises the chicks alone. Pairs may split and chose other mates during a breeding season. Indigo buntings sometimes mate with an individual that is not their partner.
Males do not sing often in courtship, but they do follow their mate around during the nest building and laying periods. They may chase other males away.
Indigo buntings breed between May and September. They may raise more than one brood during the breeding season. They may also change mates or move to a new location when they begin a second brood. The female indigo bunting chooses the nest site and builds the nest by herself. Building the nest may take her up to eight days. Nests are built in tall shrubs in fields or at the edges of woods, roadsides and railways. They are made of leaves, grasses, stems and strips of bark. After the nest is finished, the female lays 1 to 4 (usually 3 or 4) white eggs. One egg is laid each day, early in the morning. The female incubates the eggs for 11 to 14 (usually 12 to 13) days.
The chicks are helpless (altricial) when they hatch. The female must brood them for the first few days to keep them warm on cool days and protect them from the heat on hot, sunny days. She feeds the chicks insects and removes their fecal sacs from the nest. The chicks leave the nest 8 to 14 days after they hatch. They become independent about 3 weeks after they leave the nest. They may begin breeding the next summer.
The female chooses the nest site and builds the nest. She broods the chicks for the first few days after they hatch. She also feeds them insects and cleans the nest. The chicks leave the nest 8 to 14 days after they hatch. They become independent about 3 weeks after they first leave the nest. The male parent does not help incubate or raise the chicks.
Indigo buntings can live up to 10 years in the wild.
Indigo buntings are solitary. During the breeding season, males defend a territory, and one or more females will nest in each territory. During the winter, indigo buntings roost in a flock at night. During the day, they search for food alone, or small groups.
Indigo buntings are migratory. They may fly as far as 2000 miles between their wintering and breeding grounds. They leave their breeding grounds in September and October. They leave their wintering grounds to return in late April and May. They migrate mostly at night.
In one study, 10% of banded fledglings returned to breed within 1 to 2 km of their natal site (Payne 1992).
Indigo buntings use songs, calls and physical displays to communicate. Only male indigo buntings sing. Each male has one complex song that it sings during the breeding season. Males sing to defend their territory from other males and to attract females. Males may also try to attract a female by performing displays. For example, males may strut in circles in front of a female, spreading his wings and crouching his head. This display is part of courtship.
During the breeding season, indigo buntings eat small spiders and insects, seeds and berries. Common food items include caterpillars, grasshoppers, bugs, beetles, seeds and berries. In winter, indigo buntings eat small seeds, buds, and some insects. Their main food in winter is small seeds of grasses. They also commonly rice in fields where it is grown. Indigo buntings do not seem to drink very often. They probably get enough water from their food. (Payne 1992)
Indigo buntings feed alone during the breeding season. In winter, they feed in flocks. They do not store food to eat later.
Incubating females, eggs and young are eaten by climbing predators. These predators include raccoons, opossum, red fox, feral cats, blue jays and blue racers. Though adults are surely eaten too, we do not know who the predators of adults are.
Adult buntings may pretend to be injured to distract predators from their nest.
Indigo buntings affect the populations of the insects they eat. They also help distribute seeds of the plants whose berries they eat. They host at least one parasite, called hippoboscid flies (Payne 1992).
There are no known adverse affects of indigo buntings on humans.
Indigo buntings are enjoyed by bird watchers. They are also a popular pet.
Indigo buntings are becoming more common. They are not threatened or endangered, but they are protected in the United States under the U.S. Migratory Bird Treaty Act.
Indigo buntings are sometimes killed by hunters. They are also a popular as pet birds in Europe and Mexico.
Rishauna Zumberg (author), University of Michigan-Ann Arbor.
Payne, R. 1992 The Birds of North America, No.4, Indigo Bunting. A. Poole, P. Stettenheim, and F. Gill, Editors.
Robbins, Bruun, and Zim 1983, A Guide to Field Identification, Birds of North America. Golden Press.
Scientific American. 1980, Birds, W.H. Freeman and Company, San Francisco; p.68.
The New Encyclopedia Britannica, Vol.15. !986, Birds, Encyclopedia Britannica, Inc. Chicago; p. 95-96.