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Passerina cyaneaindigo bunting

By Rishauna Zumberg

Geographic Range

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.

Habitat

Indigo buntings breed in brushy and weedy habitats along the edges of farmed land, woods, road, power lines, railways and riparian habitats. They also breed in clearings in open deciduous woodlands, in weedy or abandoned agricultural fields, and in swamps. During migration they look for open grasslands and leafy trees similar to those in their winter habitat. In winter, indigo buntings choose open habitats, such as weedy fields, citrus orchards, savannas, weedy croplands and low second growth (Payne 1992).

Physical Description

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 and only a tinge of blue on their tail and shoulders. Indigo buntings are small birds, from 11.5 cm to13 cm long and weighing 12 to 18 g. They have short, conical beaks and black or gray legs and feet. (Payne 1992, Robbins, Bruun and Zim 1983)

  • Sexual Dimorphism
  • sexes colored or patterned differently
  • male more colorful
  • Range mass
    12 to 18 g
    0.42 to 0.63 oz
  • Range length
    11.5 to 13 cm
    4.53 to 5.12 in

Reproduction

Indigo buntings are socially monogamous. However, pairs only associate until incubation begins, and may switch partners within a single breeding season. Fertilizations outside of a breeding pair are not uncommon and approximately 15% of males have more than one mate.

Males do not sing often in courtship, but they do follow their mate around during the nest building and laying periods, often chasing other males away.

Indigo buntings breed between May and September, with most activity occurring June through August. They may raise more than one brood per season, and may switch nests or mates between broods. The female chooses the nest site and builds the nest, which may take up to eight days. Nests are built in shrubs in fields or at the edges of woods, roadsides and railways. They are constructed of leaves, grasses, stems and strips of bark. After the nest is complete, the female lays 1 to 4 (usually 3 or 4) white eggs. One egg is laid each day, soon after sunrise. The female begins incubating after the last egg is laid. Incubation lasts for 11 to 14 (usually 12 to 13) days.

The female broods the altricial chicks for the first few days after they hatch. She also feeds the chicks insects and removes their fecal sacs from the nest. The chicks leave the nest 8 to 14 days after hatching, and become independent about 3 weeks after fledging. Indigo buntings are sexually mature at one year old.

  • Breeding interval
    Indigo buntings breed between May and September, with most activity occurring June through August.
  • Breeding season
    Indigo buntings may raise more than one brood per season, and may switch nests or mates between broods.
  • Range eggs per season
    1 to 4
  • Average eggs per season
    3.5
  • Average eggs per season
    4
    AnAge
  • Range time to hatching
    11 to 14 days
  • Average time to hatching
    12-13 days
  • Range fledging age
    8 to 14 days
  • Average time to independence
    3 weeks
  • Range age at sexual or reproductive maturity (female)
    1 (low) years
  • Range age at sexual or reproductive maturity (male)
    1 (low) years

The male does not generally help with incubation or raising the chicks. The female chooses the nest site and builds the nest. She broods the altricial chicks for the first few days after they hatch, feeds them insects and removes their fecal sacs from the nest. The chicks leave the nest 8 to 14 days after hatching, and become independent about 3 weeks after fledging.

  • Parental Investment
  • altricial
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • provisioning
      • female
    • protecting
      • female

Lifespan/Longevity

Indigo buntings can live up to 10 years in the wild.

Behavior

Indigo buntings are generally solitary. During the breeding season, males establish and defend a territory 0.4 to 8 ha in size. Each territory may hold one or more females. During the winter, indigo buntings roost in a flock at night, but spend the days foraging alone or in small groups. There appears to be no dominance hierarchy within these groups. (Payne 1992)

Indigo buntings are migratory, and may fly as far as 2000 miles between their wintering and breeding grounds. They leave their breeding grounds in September and October, and leave their wintering grounds to return in late April and May. They migrate largely at night. (Payne 1992, Robbins, Bruun, and Zim 1983, Scientific American 1980)

  • Range territory size
    .004 to .08 km^2

Home Range

In one study, 10% of banded fledglings returned to breed within 1 to 2 km of their natal site (Payne 1992).

Communication and Perception

Indigo buntings use vocalizations and visual cues to communicate. Only male indigo buntings sing. Each male has one complex song that it sings, during the breeding season to advertise occupancy of a territory to other males and to attract females. Males may also court females by performing displays, such as the display in which a male struts in circles in front of a female with his wings spread and his head crouched.

Food Habits

During the breeding season, indigo buntings eat small spiders and insects, seeds of grasses and herbs, and berries. Major food items taken 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 frequent feeders, and eat the seeds of rice in rice fields. Indigo buntings do not appear to drink frequently, and may obtain sufficient water from their diet. (Payne 1992)

Indigo buntings feed alone during the breeding season and in flocks during the winter. They do not appear to store food for later consumption. (Payne 1992)

  • Animal Foods
  • insects
  • terrestrial non-insect arthropods
  • Plant Foods
  • seeds, grains, and nuts
  • fruit

Predation

Although predation of adult indigo buntings surely occurs, specific predators have not been identified. Brooding females, eggs and young are vulnerable to predation from climbing predators, including raccoons, opossum, red fox, feral cats, blue jays and blue racers.

When a predator approaches a nest, adult buntings may feign injury and make a chip-chip-chip call to distract the predator and lure them away from the nest. They do not mob predators.

Ecosystem Roles

Perching birds (order Passeriformes) as a group play an important role in the earth's ecosystems. They consume many varieties and amounts of food and serve as food for others and hosts for parasites (Britannica, 1986). Indigo buntings affect the populations of the insects they eat, and help distribute seeds of the plants whose berries they eat. They also host at least one parasite; hippoboscid flies (Payne 1992).

  • Ecosystem Impact
  • disperses seeds

Economic Importance for Humans: Positive

There is apparent aesthetic importance of songbirds like the Indigo bunting to bird watchers and listeners. This brightly colored species is commonly kept as a cage bird (Britannica, 1986).

Economic Importance for Humans: Negative

There are no known adverse affects of indigo buntings on humans.

Conservation Status

Indigo buntings appear to be increasing in geographic range and density. They are protected under the U.S. Migratory Bird Act, but not under CITES or the U.S. Endangered Species Act.

Indigo buntings are occasionally killed for sport and food. They are also a popular cage bird in Europe and Mexico. (Payne, 1992)

Contributors

Rishauna Zumberg (author), University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

arboreal

Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

diurnal
  1. active during the day, 2. lasting for one day.
endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

migratory

makes seasonal movements between breeding and wintering grounds

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

omnivore

an animal that mainly eats all kinds of things, including plants and animals

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

visual

uses sight to communicate

References

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.

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