The Indigo Bunting (Passerina cyanea), a sparrow-sized songbird, is known for its vibrant blue plumage in males and its adaptability to various habitats. This article delves into the dietary habits and foraging behaviors of the Indigo Bunting, exploring how these aspects contribute to its survival and ecological role.
Physical Characteristics
The Indigo Bunting is a small bird, averaging 12-13 cm in length, with a wingspan of 19-22 cm and weighing between 12-18 grams. Adult males are a striking bright blue color, with darker coloration on their outer wings and a richer blue on their head. Females and juveniles are brown, with occasional light blue streaking, a lighter colored chest, and a white throat. The bird is a constant singer from the time it arrives until the second brood is out of the nest, and it sings volubly during the hottest part of the day, usually selecting the top of some small tree and repeating its song many times before it seeks another perch.
Habitat and Distribution
Indigo Buntings inhabit brushy and weedy areas, including woodland borders, overgrown fields, shrubby swamps, upland old fields, and mesic forests. They are commonly found along roads, streams, rivers, and powerline cuts, as well as in logged forest plots, brushy canyons, and abandoned fields. Their breeding range extends across the eastern US, parts of the southwestern US, and southern Canada. During winter, they migrate to southern Mexico, Central America, southern Florida, and the Caribbean.
Foraging Behavior
Indigo Buntings forage on the ground and in low foliage for insects, weed seeds, wild berries, and grains. They are often seen feeding from ground level up to 15 meters, taking insects from vegetation within the tree canopy. During the breeding season, they forage in trees within their song site, alternating between feeding and singing.
Seasonal Diet
The Indigo Bunting's diet varies depending on the season. During the breeding season, when it is warm, their diet consists mostly of spiders and insects, including grasshoppers, caterpillars, and beetles. They also consume berries and some seeds. In winter, they primarily eat seeds that have dropped from grasses or on the seed head, as well as berries.
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Summer Diet
In the summer months, insects and spiders form the majority of the Indigo Bunting's diet. Common insect prey includes caterpillars, grasshoppers, aphids, cicadas, and beetles such as canker worms, click beetles, and weevils. They may also consume berries such as blueberries, strawberries, blackberries, serviceberries, and elderberries.
Winter Diet
During the winter, seeds become a staple food source for Indigo Buntings. They eat seeds of herbs and grasses, including thistles, dandelions, goldenrods, and grains such as oats. They also consume wild berries when available.
Food Preferences at Feeders
Indigo Buntings can be attracted to bird feeders with a variety of seeds. Preferred foods include white millet, nyjer (thistle seed), sunflower hearts and chips, other millets, oil sunflower, cracked corn, roasted peanut chips, milo, wheat, rye, and oats. They will readily eat alongside Goldfinches at finch feeders filled with WBU Finch Mix, which contains nyjer and sunflower chips. They may also eat white millet or sunflower chips from tray, tube, or hopper feeders, as long as they aren't ousted by more dominant birds.
Nesting and Diet of Young
During the breeding season, female Indigo Buntings arrive from migration a couple of days later than the males and settle on a nest site within two days after choosing a territory. The females then build a nest, which can take from two to eight days to complete. They build it alone, up to one meter from the ground on sites with low, branching vegetation in fields, near the edges of woods, roadsides, and in understory shrub. The nest is an open cup of soft leaves, coarse grasses, stems, and strips of bark held together with a weaving of spider web and lined with finer materials such as slender grasses, rootlets, and thistle. Clutch size is about three eggs, mostly white with 1% possessing fleck marks. The female Indigo Bunting is inattentive to the nest until last egg is lain, then she will incubate the eggs while the male bird remains uninvolved, except for his chirping when there is an intruder and when the eggs hatch. This bird species has 1-3 broods, and eggs hatch in 11-14 days, depending on the temperature. The hatched birds remain nestlings for 8-14 days. Young in the nest are fed mostly insects at first. The male sometimes takes over feeding of fledged young while female begins second nesting attempt.
Conservation Status and Threats
Indigo Buntings are generally abundant throughout their range, though populations have declined yearly by an estimated 0.62% for a cumulative decline of about 28% between 1966 and 2019, according to the North American Breeding Bird Survey. Partners in Flight estimates a global breeding population of 77 million and rates them 9 out of 20 on the Continental Concern Score, indicating a species of low conservation concern. Indigo Bunting populations decrease with intensive agriculture, reforestation, frequent mowing of roadsides and fields, and increasing urbanization; they increase with the expansion of shrubby, weedy habitat. The males' showy plumage can be a handicap, as these bright blue birds are prized as cage birds in parts of Mexico, where they have been trapped for illegal sale. Unfortunately, Indigo Buntings and many other small birds are commonly hunted on their tropical wintering grounds. During migration, many die after flying into buildings and transmission towers. These birds breed and sing along roadsides, and collisions with vehicles kill many birds in summer.
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