Content for this page researched and created by Danielle Leeman

The Indigo Bunting (Passerina cyanea) is a small bird of the family Cardinalidae. It weighs approximately 0.4-0.6 ounces, with a length of 4.77-5.1 inches and wingspan of 7.5-8.7 inches (All About Birds). During breeding season, adult males appear to have bright blue feathers that can look black in some lighting. The head and wings are a darker blue than the body. Interestingly, the feathers contain no blue pigment at all, but seem blue due to the diffraction of light (Deinlein). Immature males tend to be mostly blue with some brown throughout. Females are dull grey-brown with some streaking on the breast and a white throat and belly. This difference between male and female appearance is called sexual dimorphism. Males

look similar to females or immature males when not breeding. Male Indigo Buntings can be mistaken for Blue Grosbeaks; however, the bunting is smaller and has slightly different coloration. They also molt their feathers twice every year (Dwight) and have short, black and silver, cone-shaped beaks (Wildscreen Arkive). The Indigo Bunting diet varies slightly depending on the season and what is available. Their diet consists mainly of spiders, insects, and seeds, as well as buds of plants and berries (Zumberg). Their short, conical beaks are great for breaking and eating seeds.

Indigo Buntings are migratory birds. They breed during the late spring and early summer, typically between May and August (Wildscreen Arkive). Breeding can occur in many places throughout the eastern United States and southern Canada, although they have also been spotted in western states as far as California. Migration can take place between September and November, traveling to Mexico, South and Central America, the West Indies, and occasionally staying in the southern states such as Florida (Encyclopedia of Life). They can travel up to 2000 km to their winter destination and will often return to the area where they were born for the next breeding season (Payne 2016). However, females rarely mate within the area where they were born (“A Genetic and Behavioral Analysis”). During breeding season, Indigo Buntings are solitary birds and roost alone. While migrating, they will flock, travel, and gather food together. Indigo Buntings also use the stars to navigate. They observe the patterns of stars around the north star, as well as use the sun, wind, smells, and landmarks to gauge direction and orient themselves (Deinlein).

Indigo Buntings prefer a habitat close to the ground in the cover of thick brush and grasses, although the males will frequently be found singing on the tops of tall trees and telephone lines. They can be found in shrubby areas such as on roadsides and the edges of forests in thickets, as well as in open fields with plenty of vegetation. Although

they seem to favor this type of environment, they have also been found in swamplands and near water sources. The Indigo Bunting population has seen a 31% decrease between 1966 and 2014 due to an increase in crop cultivation, reforestation, and mowing (All About Birds). However, they have been thriving in areas where deforestation, woodland clearings, and wildfires have occurred. Many other species have lost their habitats due to this destruction, but the Indigo Buntings use it to their advantage. This species also does not prevail in edge habitats, and fewer young tend to be fledged in such areas (Weldon). Generally, Indigo Buntings have short life spans, and females have been shown to have lower survival estimates than males (“Survival Estimates of Indigo Buntings”).

The females are a relatively elusive bird, tending to stay in the concealment of plants where they build the nest. Nests are almost exclusively built by the female during breeding season, and males provide little to no parental care (Ritchison), although they do protect the nest from predators. At times, the resident male is even excluded by the young (Westneat). The nests are built around one meter from the ground in the forked branches of small shrubs. They are constructed as woven cups of leaves, grasses, animal hair, bark, and down (All About Birds). The female typically lays three to four small eggs in one brood. The eggs, typically all white with no markings (Arnold), are incubated for 12-13 days, and the newly hatched birds will remain in the nest for around 9-13 more days under the care of the mother before fledging. These hatchlings are pinkish orange in color, some with small amounts of grey natal down (Bent). Regarding mating, Indigo Buntings may be monogamous or polygynous, although polygyny may cause lower offspring success due to the male being split between multiple nests, not able to protect the nests as well (Carey). Predators that may try to take the young or eggs include animals such as raccoons, opossum, cats, foxes, and blue jays. The mother is also vulnerable to these predators while she is caring for the eggs or hatchlings (Encyclopedia of Life).

Indigo Buntings experience brood parasitism by Cowbirds. A mother Cowbird may drop one or two of her eggs into an Indigo Bunting (host) nest, leaving it in the care of the female Indigo Bunting. This can cause a lower breeding success for the Indigo Bunting for many reasons. The Cowbird often removes an egg from the host nest before leaving her

own egg. Also, there will be an increase in competition between the young. Most of the time, the Indigo Bunting mother will care for the Cowbird egg as her own, so the hatchlings will be competing for care. The male Indigo Bunting generally does not try to remove the parasitic egg because it does not want to harm any of its own eggs in the process (“Brood Parasitism by Cowbirds”). If the nest is parasitized before the nest is finished being built, the host mother may abandon the nest or cover them by building a layer of nest on top of the Cowbird eggs (Bent).

The Indigo Bunting’s call has been widely studied in the scientific community. Studies have shown that young males copy the songs of adult males in the same area. However, they do not copy their father’s song. This song mimicry creates song neighborhoods, which means that, in a given area, males will be singing the same or similar songs. Song learning is highly social in this species. An experiment was conducted where some birds were isolated alone, and others were isolated in groups. The individuals that were isolated alone developed abnormal songs, while those in groups developed slightly more normal songs, although they did not completely resemble a wild adult’s song (“Song Learning and Social Interaction”). This shows how Indigo Buntings develop their songs from being around other birds, and without that social aspect, they will not develop correctly. Copying songs has been shown to be advantageous to young males. Young males who copy the songs of older males are more successful in mating, nesting, and fledging young. They may also be able to trick their competitors into thinking they are adult males that have claimed a territory, which is also more appealing to prospective mates (“The Social Context of Song Mimicry”).

According the Johns, “The male bunting’s song consists of a rapid series of high-pitched buzzy notes that are delivered in pairs, like–“sweet-sweet, zweet-zweet, sayt-sayt, zeet-zeet–with every other pair of notes harsher and more strident than the preceding couplet” (Wildlife Profile). Males have very complex, organized songs and use different tones and notes to communicate. Sharper sounds are used when the nest is in danger, and high-pitched buzzes are a form of communication when flying. The male spends much of the day singing its long, complex song to attract mates and mark its territory (Ayre). Songs have been found to be shorter before pairing occurs and after the young leave the nest and longer during nest building (Beckett).

 

General References:

Arnold, Keith A. “Indigo Bunting.” The Texas Breeding Bird Atlas. Texas A&M University, n.d. Web. 23 Sept. 2016.

Ayre, James. “Indigo Bunting.” PlanetSave. Sustainable Enterprises Media, Inc., 24 May 2013. Web. 25 Sept. 2016.

Bent, Arthur Cleveland. “Indigo Bunting.” Life Histories of Familiar North American Birds. Smithsonian Institution, 1968. Web. 25 Sept. 2016.

Deinlein, Mary. “A Stellar Migrant.” Smithsonian Migratory Bird Center. Smithsonian Institution, 1 July 1997. Web. 23 Sept. 2016.

“Indigo Bunting.” All About Birds. Cornell University, 2015. Web. 23 Sept. 2016.

“Indigo Bunting.” Wildscreen Arkive. N.p., n.d. Web. 23 Sept. 2016.

Johns, Mark. “Indigo Bunting (Passerina Cyanea).” Wildlife Profile. N.p., n.d. Web. 25 Sept. 2016.

“Passerina Cyanea (Indigo Bunting).” Encyclopedia of Life. N.p., n.d. Web. 23 Sept. 2016.

Payne, Robert B. “Indigo Bunting.” Birds of North America. Cornell University, 1 Oct. 2006. Web. 23 Sept. 2016.

Zumberg, Rishauna. “Passerina Cyanea (Indigo Bunting).” Animal Diversity Web. University of Michigan, 1999. Web. 23 Sept. 2016.

 

Scientific References:

Beckett, Matthew D., and Gary Ritchison. “Effects of Breeding Stage and Behavioral Context on Singing Behavior of Male Indigo Buntings.” The Wilson Journal of Ornithology 122.4 (2010): 655-65. BioOne. Web. 25 Sept. 2016.

Carey, Michael, and Val Nolan, Jr. “Population Dynamics of Indigo Buntings and the Evolution of Avian Polygyny.” Evolution 33.4 (1979): 1180-1192. JSTOR. Web. 25 Sept. 2016.

Dwight, Jonathan. “The Plumages and Molts of the Indigo Bunting (Passerina Cyanea).” Science 11.277 (1900): 627-30. JSTOR. Web. 25 Sept. 2016.

Payne, Robert B., and David Westneat F. “A Genetic and Behavioral Analysis of Mate Choice and Song Neighborhoods in Indigo Buntings.” Evolution 42.5 (1988): 935-47. JSTOR. Web. 25 Sept. 2016.

Payne, Robert B., and Laura Payne L. “Brood Parasitism by Cowbirds: Risks and Effects on Reproductive Success and Survival in Indigo Buntings.” Behavioral Ecology 9.1 (1998): 64-73. Oxford Journals. Web. 25 Sept. 2016.

Payne, Robert B., and Laura Payne L. “Survival Estimates of Indigo Buntings: Comparison of Banding Recoveries and Local Observations.” The Condor 92.4 (1990): 938-46. JSTOR. Web. 25 Sept. 2016.

Payne, Robert B. “Natal Dispersal and Population Structure in a Migratory Songbird, The Indigo Bunting.” Evolution 45.1 (1991): 49-62. JSTOR. Web. 25 Sept. 2016.

Payne, Robert B. “Song Learning and Social Interaction in Indigo Buntings.” Animal Behavior 29.3 (1981): 688-97. Science Direct. Web. 25 Sept. 2016.

Payne, Robert B. “The Social Context of Song Mimicry: Song-matching Dialects in Indigo Buntings (Passerina Cyanea).” Animal Behavior 31.3 (1983): 788-805. ScienceDirect. Web. 25 Sept. 2016.

Ritchison, Gary, and Kimberly Little P. “Provisioning Behavior of Male and Female Indigo Buntings.” The Wilson Journal of Ornithology 126.2 (2014): 370-373. BioOne. Web. 25 Sept. 2016.

Weldon, Aimee J., and Nick Haddad M. “The Effects of Patch Shape on Indigo Buntings: Evidence for an Ecological Trap.” Ecology 86.6 (2005): 1422-431. JSTOR. Web. 25 Sept. 2016.

Westneat, David F. “Genetic Parentage in the Indigo Bunting: A Study Using DNA Fingerprinting.” Behavioral Ecology and Sociobiology 27.1 (1990): 67-76. JSTOR. Web. 25 Sept. 2016.

 

Image Gallery:

(images used via Creative Commons)

Bonnett, Richard. Indigo Bunting Nest. Digital image. Flickr. N.p., 7 June 2009. Web. 25 Sept. 2016.

Flannery, John. Indigo Bunting. Digital image. Flikr. N.p., 29 Apr. 2014. Web. 25 Sept. 2016.

Phoward2009. Immature Indigo Bunting. Digital image. Flikr. N.p., 24 Feb. 2011. Web. 25 Sept. 2016.

Schmierer, Alan. 924 – INDIGO BUNTING (2-4-10) Bentsen-rio Grande State Park, Tx (5). Digital image. Flikr. N.p., 4 Feb. 2010. Web. 25 Sept. 2016.

Seabamirum. Indigo Bunting. Digital image. Flikr. N.p., 3 Aug. 2008. Web. 25 Sept. 2016.