The Indigo Bunting is a small, vibrantly blue songbird of eastern North America. With its brilliant, shimmering plumage, it is one of the most colorful birds in North America. The Indigo Bunting belongs to the family Cardinalidae and is closely related to other finches and grosbeaks. Here is a comprehensive overview of this stunning little songbird.
Scientific Classification
The Indigo Bunting has the following scientific classification:
- Kingdom: Animalia
- Phylum: Chordata
- Class: Aves
- Order: Passeriformes
- Family: Cardinalidae
- Genus: Passerina
- Species: Passerina cyanea
It belongs to the genus Passerina, which includes other small North American songbirds like the Lazuli Bunting and Varied Bunting. Its species name “cyanea” comes from the Greek word meaning “dark blue.”
Identification
The adult male Indigo Bunting is a brilliant, shimmering blue color over most of its body. Its wings and tail are blackish blue. The color comes from microscopic structures in its feathers that refract blue light. In poor lighting conditions, it can look almost black. The beak is short and conical.
Females are mostly brown with some blue visible in their wings and tail. The brown color provides good camouflage when the female is incubating eggs in a nest. Immature males may also have brownish plumage before molting into their blue adult feathers.
Indigo Buntings are small birds, measuring 11.5-13 cm (4.5-5 inches) in length with a wingspan of 18-23 cm (7-9 inches). They weigh between 11-21 g (0.4-0.7 oz).
Distinguishing Features
Distinguishing features of the Indigo Bunting include:
- Brilliant blue plumage in breeding males
- Mostly brown coloration in females
- Small finch-like beak
- Blackish wings and tail
- Small size and compact shape
- Cheery song
Range and Habitat
Indigo Buntings breed across most of eastern North America. Their breeding range stretches west to Nebraska, Kansas, Oklahoma and Texas. They winter in southern Florida, Mexico, Central America, and the Caribbean islands.
During the summer breeding season, Indigo Buntings inhabit open shrubby areas like forest edges, power line corridors, roadsides, and agricultural areas with shrubs and small trees. They are often found along streams or wetlands. They prefer areas with dense vegetation low to the ground.
In their wintering grounds, they occur in open and semi-open habitats like scrub, agricultural fields, forest edges, and gardens.
Migration
Indigo Buntings are long distance migrants, traveling between their breeding and wintering grounds each year. They migrate at night when the air is cooler and calmer. During spring migration, the males arrive back on the breeding grounds first, followed by the females a week or two later.
Their spring migration takes place from late April through May. Fall migration occurs from late August through October as they travel back to their wintering grounds.
Diet
Indigo Buntings are primarily seed eaters. During the breeding season, they mainly eat small seeds from various weeds, grasses and other plants such as pigweed, crabgrass, clover, vetch and wheat. They sometimes supplement their diet with insects like beetles, caterpillars, wasps, grasshoppers and spiders.
They forage for food on the ground or in vegetation, sometimes hovering briefly to pick seeds. They may make short flights from low perches to catch insects. At bird feeders, they will feed on small seeds like millet.
Feeding Behavior
Some interesting facts about the feeding behavior of Indigo Buntings include:
- Forage mostly on the ground or in low vegetation
- Glean insects from foliage or capture them in short flights
- Hammer seeds with their beak to open them
- Have a diet primarily composed of small seeds during the breeding season
- Supplement their diet with insects when feeding young
- Visit bird feeders for small seeds like millet
Breeding and Nesting
Indigo Buntings breed from May to July across eastern North America. They are generally monogamous and may pair up with the same mate in subsequent breeding seasons.
The male establishes and defends a breeding territory, using song to advertise to females and ward off intruding males. His bright blue plumage is believed to play a role in mate attraction.
The female builds the nest using grasses, stems, bark strips and leaves. She chooses a nest site in a shrub or small tree or sapling, usually 1-10 feet above ground. The nest is an open cup shape with materials loosely woven together.
She lays 3-4 pale blue eggs and incubates them for 11-14 days. The altricial hatchlings are cared for by both parents. The young leave the nest about 9-12 days after hatching.
Interesting Nesting Facts
- Nest is built by female
- Open cup nest in shrub or small tree
- 3-4 pale blue eggs
- Incubation lasts 11-14 days
- Young fledge 9-12 days after hatching
- Pairs may mate together in subsequent seasons
- Male has bright “breeding plumage” to attract female
Behavior and Communication
Indigo Buntings exhibit some interesting behaviors and communication methods. The males sing loudly from high exposed perches to mark their territory and attract females. Their song is a high-pitched, buzzy “sweee-sweee-sweee-seet-seet-seet.”
The females sing much less frequently. They use a soft chip note to communicate with their mate and offspring. When alarmed, Indigo Buntings may give a sharp “tink” call note.
During migration, Indigo Buntings form large concentrated flocks that travel together. However, they are territorial on the breeding grounds with males defending areas of shrubby habitat.
They often spread their tail and hold their body horizontally when singing. They can aggressively fight with intruding Indigo Buntings by grappling feet to feet while in flight.
Cool Behaviors
- Males sing loudly to defend territories and attract mates
- Spread tail and hold body flat when singing
- Fly upward singingly sharply to deter intruders
- Males are smaller and more aggressive than females
- Form large migratory flocks
- Females use soft chip notes
- Sharp “tink” alarm note
Population and Conservation Status
According to the IUCN Red List, Indigo Buntings have a global population of 17 million and are classified as Least Concern. Their numbers increased by an estimated 16% between 1966-2015, according to the North American Breeding Bird Survey.
However, Indigo Bunting populations face threats from habitat loss, degradation, and fragmentation throughout their breeding range. Agricultural intensification and declining pasturelands reduce suitable shrubby habitat. Pesticides may reduce insect prey and nesting success.
Climate change may also pose long-term threats by altering habitat and migration patterns. Despite threats, their ability to use human-altered habitat has allowed Indigo Bunting populations to remain relatively healthy.
Population Status
- Global population 17 million
- IUCN status: Least Concern
- Increased by 16% from 1966-2015 in North America
- Uses human-altered habitat well
- Threats from habitat loss, pesticides, climate change
Fun Facts
Here are some fun and interesting facts about the dazzling Indigo Bunting:
- The Indigo Bunting molts all its feathers each year after breeding season. Molt begins mid-June and completes by early October.
- The bright blue breeding plumage of male Indigo Buntings comes from microscopic structures in their feathers that refract blue light. This is called structural coloration.
- Their brilliant blue coloring makes them popular cage birds in Mexico. This practice is now illegal under Mexican law.
- Indigo Buntings cannot digest kernel corn. They will spit it out after trying unsuccessfully to crack the kernels with their beak.
- The oldest recorded Indigo Bunting was over 10 years old. Most only live 2-3 years.
- They get their name not from the primary color indigo, but from indig, an old English word meaning dark blue.
- John James Audubon painted an Indigo Bunting for his famous Birds of America series in 1828.
Conclusion
With its vibrant blue coloring, cheery song, and engaging behaviors, the Indigo Bunting is a beloved little songbird. While it faces some conservation threats from habitat loss and other factors, it remains common across eastern North America thanks to its ability to thrive in human-altered environments.
Understanding details about its identification, range, ecology, reproduction, and behaviors provides deeper insight into the natural history of this species. The Indigo Bunting is a true avian jewel of the eastern forests and shrublands.