Indigo bunting

Last updated

Indigo bunting
Indigo Bunting by Dan Pancamo 4.jpg
Male at Quintana, Texas, spring migration
Indigo Bunting Female by Dan Pancamo 1.jpg
Female
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Passeriformes
Family: Cardinalidae
Genus: Passerina
Species:
P. cyanea
Binomial name
Passerina cyanea
(Linnaeus, 1766)
IndigoBuntingRangeMapCropped.png
Range of the indigo bunting
  Summer-only range
  Migratory range
  Winter-only range
Synonyms
  • Tanagra cyaneaLinnaeus, 1766
  • Cyanospiza cyanea(Linnaeus, 1758)

The indigo bunting (Passerina cyanea) is a small seed-eating bird in the cardinal family, Cardinalidae. It is migratory, ranging from southern Canada to northern Florida during the breeding season, and from southern Florida to northern South America during the winter. It often migrates by night, using the stars to navigate. Its habitat is farmland, brush areas, and open woodland. The indigo bunting is closely related to the lazuli bunting and interbreeds with the species where their ranges overlap.

Contents

The indigo bunting is a small bird, measuring 11.5–13 cm (4.5–5.1 in) in length. It displays sexual dimorphism in its coloration; the male is vibrant blue in the summer, with brightly colored plumage during the breeding season to attract a mate. It is brown during the winter months, while the female is brown year-round. Nest-building and incubation are done solely by the female. The diet of the indigo bunting consists primarily of insects during the summer months and seeds during the winter months.

Taxonomy

Illustration of male and female indigo bunting between 1910 and 1914. Passerina cyaneaAAP086CA.jpg
Illustration of male and female indigo bunting between 1910 and 1914.

The indigo bunting is included in the family Cardinalidae, which is made up of passerine birds found in North and South America, and is one of seven birds in the genus Passerina . [2] It was originally described as Tanagra cyanea by Linnaeus in his 18th-century work, Systema Naturae . The current genus name, Passerina, is derived from the Latin term passer for true sparrows and similar small birds, [3] while the species name, cyanea, is Latin for cyan, the color of the male's breeding plumage. [4]

The indigo bunting is a close relative of the lazuli bunting and interbreeds with the species where their ranges overlap, in the Great Plains. [5] They were declared to form a superspecies by the American Ornithologists' Union in 1983. [6] However, according to sequencing of the mitochondrial cytochrome-b gene of members of the genus Passerina, it was determined that the indigo bunting and lazuli bunting are not, in fact, sister taxa. The indigo bunting is the sister of two sister groups, a "blue" (lazuli bunting and blue grosbeak) and a "painted" (rose-bellied bunting, orange-breasted bunting, varied bunting, and painted bunting) clade. This genetic study shows these species diverged between 4.1 and 7.3 million years ago. This timing, which is consistent with fossil evidence, coincides with a late-Miocene cooling, which caused the evolution of a variety of western grassland habitats. Evolving to reduce size may have allowed buntings to exploit grass seeds as a food source. [7]

Description

Juvenile male indigo bunting at Smith Oaks Sanctuary, High Island, Texas Indigo bunting at Smith Oaks Sanctuary, High Island.jpg
Juvenile male indigo bunting at Smith Oaks Sanctuary, High Island, Texas

The indigo bunting is a smallish songbird, around the size of a small sparrow. It measures 11.5–15 cm (4.5–5.9 in) long, with a wingspan of 18–23 cm (7.1–9.1 in). [8] [9] Body mass averages 14.5 g (0.51 oz), with a reported range of 11.2–21.4 g (0.40–0.75 oz). [10] During the breeding season, the adult male appears mostly a vibrant cerulean blue. Only the head is indigo. The wings and tail are black with cerulean blue edges. In fall and winter plumage, the male has brown edges to the blue body and head feathers, which overlap to make the bird appear mostly brown. The adult female is brown on the upperparts and lighter brown on the underparts. It has indistinct wing bars and is faintly streaked with darker markings underneath. [11] The immature bird resembles the female in coloring, although a male may have hints of blue on the tail and shoulders and have darker streaks on the underside. The beak is short and conical. In the adult female, the beak is light brown tinged with blue, and in the adult male the upper half is brownish-black while the lower is light blue. [12] The feet and legs are black or gray. [13]

First years and adult males are distinguishable through close observations of the skull and its degree of ossification. Juvenile skulls have a slightly pinkish color that gives under pressure due to its singular layer. Adults instead have a double layer skull, which gives more resistance when applying pressure. First year birds also tend to have a fleshy, yellow gape in the corner of the mouth, apparent in all months except October and November. When comparing males to females that both have brown molt, increased wing length and weight typically indicate a bunting is a male. [14]

As indicated by data collected from Charles H. Blake from his banding experiments in Hillsborough, NC, the Indigo Bunting has a weighted annual survival rate of 0.585. Using his own methods (Blake 1967, p. 5) and a pool of 25 indigo buntings captured and observed, it was determined that approximately two out of twenty-five indigo buntings should live up to six years. Using the calculated annual rate of six-year-old birds obtained (2/25 = 0.08), an annual rate of 0.656 was calculated, 12% higher than the annual rate of 0.585, leading to the 1 out of 25 statistic. The oldest recorded bunting was at least 13 years and 3 months old. [15] However, not much emphasis should be placed on these values since the pool of individuals is small, where any individual can affect the weighted average. [16]

Distribution and habitat

The habitat of the indigo bunting is brushy forest edges, open deciduous woods, second growth woodland, and farmland. [17] Increases in population size have been seen in the event of forest clearings and development of land into farms. [18] The breeding range stretches from southern Canada to Maine, south to northern Florida and eastern Texas, and westward to southern Nevada. The winter range begins in southern Florida and central Mexico and stretches south through the West Indies and Central America to northern South America. [9] It has occurred as a vagrant in Antigua and Barbuda, Barbados, Denmark, Ecuador, Germany, Iceland, Ireland, Netherlands, the Netherlands Antilles, Saint Pierre and Miquelon, Serbia and the United Kingdom. [19]

Ecology and behavior

Vocalizations

The indigo bunting communicates through vocalizations and visual cues. A sharp chip! call is used by both sexes, and is used as an alarm call if a nest or chick is threatened. A high-pitched, buzzed zeeep is used as a contact call when the indigo bunting is in flight. [20] The song of the male bird is a high-pitched buzzed sweet-sweet chew-chew sweet-sweet, lasting two to four seconds, sung to mark his territory to other males and to attract females. Each male has a single complex song, [13] which he sings while perched on elevated objects, such as posts, wires, and bush-tops. [21] In areas where the ranges of the lazuli bunting and the indigo bunting overlap, the males defend territories from each another. [22]

Migration

Migration takes place in April and May and then again in September and October. [9] Previous research indicates that towards the end of August there is a spike in migration, indicated by a rapid surge of captures in the last ten days of August. Migration activities peak in late September and fall off rapidly as October approaches. Only a small percentage of buntings remain as summer residents instead of migrating (7.2% of banded birds in Burke's observation). [16]

The indigo bunting often migrates during the night, using the stars to navigate. [23] This is not an unusual proposal, for many other birds such as the blackcaps or red-backed shrikes were used to test if birds have orientated migratory behavior or Zugunruhe. Research indicates that indigo buntings placed in funnel cages outside on cloudless autumn nights or in artificial planetariums made more southern directional choices. When introduced to increasingly overcast nights, many bunting's abilities to distinctively make southern directional changes decreased, possibly indicating a negative correlation between Zugunruhe and cloud coverage. When in the artificial planetarium scenario and in the presence of a magnetic field similar to Earth's, birds were unable to orientate themselves in a no-star environment, indicating that past hypotheses supporting that birds use geophysical clues as well may be incorrect. [24]

Indigo buntings do not rely on individual stars or the general brightness of groups of stars, but instead use them as clues in navigation. Prior experiments removing certain constellations and stars (Big Dipper, Cassiopeia or Polaris) from the sky had minimal effect on Zugunruhe. Indigo buntings do use the northern sky to help navigate both in the fall and in the spring. It was thought that the bunting has an internal clock, being able to compensate for the movement of stars. However, temporal compensation for stellar motion is not a part of their migratory methods. [25]

In captivity, since it cannot migrate, it experiences disorientation in April and May and in September and October if it cannot see the stars from its enclosure. [9]

While debate has occurred over the years about how birds migrate near the Gulf of Mexico, indigo buntings migrate to South America by flying both over the Gulf of Mexico and around the Gulf of Mexico, with a majority of buntings choosing the trans-Gulf path. Past evidence indicated that indigo buntings did not have a high enough fat content to travel across the Gulf, but that evidence is misleading since most of those birds supporting that study were immature, not having a high body fat content. [18]

Since indigo buntings and many other birds are at their lightest after mating season, questions arose whether increases in overall weight were attributed to fat or other factors such as water weight, or carbohydrates. Research indicates that most if not all weight gain is a gain in fat content. [18]

Quantitative methods of estimating flight range instead look at metabolic rates of the bunting and how much fat it has to use as fuel. Research indicates that the metabolic rate of a lean 13 g (0.46 oz) indigo bunting is 0.64 kcal/hour. With an average speed of 20 mph, 5 extra grams of fat (47.5 kcal of energy) extends a bunting's range to six hundred and eighty-eight miles (1,107 km). 19 g (0.67 oz) is equivalent to eight hundred and twenty-six miles (1,329 km). Given that the trip across the Gulf of Mexico from Florida is approximately six hundred miles (966 km), buntings weighing at least 18 g could make the trip without any stops. [18]

Breeding

Indigo bunting nest and egg laying. Indigo Bunting nest.jpg
Indigo bunting nest and egg laying.

These birds are generally monogamous but not always faithful to their partner. In the western part of their range, they often hybridize with the lazuli bunting. Nesting sites are located in dense shrub or a low tree, generally 0.3–1 m (0.98–3.28 ft) above the ground, but rarely up to 9 m (30 ft). [22] The nest itself is constructed of leaves, coarse grasses, stems, and strips of bark, lined with soft grass or deer hair and is bound with spider web. It is constructed by the female, who cares for the eggs alone. [22] The clutch consists of one to four eggs, but usually contains three to four. The eggs are white and usually unmarked, though some may be marked with brownish spots, averaging 18.7 mm × 13.7 mm (0.74 in × 0.54 in) in size. [26] The eggs are incubated for 12 to 13 days and the chicks are altricial at hatching. [9] Chicks fledge 10 to 12 days after hatching. Most pairs raise two broods per year, and the male may feed newly fledged young while the females incubate the next clutch of eggs. [27]

The brown-headed cowbird may parasitize this species. [8] Indigo buntings abandon their nest if a cowbird egg appears before they lay any of their own eggs, but accept the egg after that point. Pairs with parasitized nests have less reproductive success. The bunting chicks hatch, but have lower survival rates as they must compete with the cowbird chick for food. [28]

Diet

The indigo bunting forages for food on the ground or in trees or shrubs. [22] In winter, it often feeds in flocks with other indigo buntings, but is a solitary feeder during the breeding season. [13] During the breeding season, the species eats seeds of grasses and herbs, berries, spiders and insects, including caterpillars, grasshoppers, true bugs, and beetles. [13] The seeds of grasses are the mainstay of its diet during the winter, although buds and insects are eaten when available. The young are fed mainly insects at first, to provide them with protein. [22] The indigo bunting does not drink frequently, generally obtaining sufficient water from its diet. [13]

Predators and parasites

Indigo bunting nests are vulnerable to a variety of climbing and flying predators, including Virginia opossum (Didelphis virginiana), red fox (Vulpes vulpes), domestic cat (Felis catus), blue jay (Cyanocitta cristata), eastern racer (Coluber constrictor) and raccoon (Procyon lotor). [22] The bird is also susceptible to parasitism by louse flies. [29]

Conservation status

The criteria for a change in conservation status are a decline of more than 30% in ten years or over three generations. [19] The species is classified as being of least concern according to the International Union for Conservation of Nature, with an estimated range of 5,900,000 km2 (2,300,000 sq mi) and a population of 28 million individuals. Global population trends have not been quantified, but the species is not believed to approach the thresholds for a population decline warranting an upgrade in conservation status. [19]

Related Research Articles

<span class="mw-page-title-main">Black-throated loon</span> Migratory aquatic bird found in the northern hemisphere

The black-throated loon, also known as the Arctic loon and the black-throated diver, is a migratory aquatic bird found in the northern hemisphere, primarily breeding in freshwater lakes in northern Europe and Asia. It winters along sheltered, ice-free coasts of the north-east Atlantic Ocean and the eastern and western Pacific Ocean. This loon was first described by Carl Linnaeus in 1758 and has two subspecies. It was previously considered to be the same species as the Pacific loon, of which it is traditionally considered to be a sister species, although this is debated. In a study that used mitochondrial and nuclear intron DNA, the black-throated loon was found to be sister to a clade consisting of the Pacific loon and two sister species, the common loon and the yellow-billed loon.

<span class="mw-page-title-main">Cardinalidae</span> Bird family

Cardinalidae is a family of New World-endemic passerine birds that consists of cardinals, grosbeaks, and buntings. It also includes several other genera such as the tanager-like Piranga and the warbler-like Granatellus. Membership of this family is not easily defined by a single or even a set of physical characteristics, but instead by molecular work. Among songbirds, they range from average-sized to relatively large, and have stout features, some species with large, heavy bills.

<span class="mw-page-title-main">Killdeer</span> Shorebird found in the Americas

The killdeer is a large plover found in the Americas. It gets its name from its shrill, two-syllable call, which is often heard. It was described and given its current scientific name in 1758 by Carl Linnaeus in the 10th edition of his Systema Naturae. Three subspecies are described. Its upperparts are mostly brown with rufous fringes, the head has patches of white and black, and two black bands cross the breast. The belly and the rest of the breast are white. The nominate subspecies breeds from southeastern Alaska and southern Canada to Mexico. It is seen year-round in the southern half of its breeding range; the subspecies C. v. ternominatus is resident in the West Indies, and C. v. peruvianus inhabits Peru and surrounding South American countries throughout the year. North American breeders winter from their resident range south to Central America, the West Indies, and the northernmost portions of South America.

<span class="mw-page-title-main">Razorbill</span> Species of auk

The razorbill is a North Atlantic colonial seabird and the only extant member of the genus Alca of the family Alcidae, the auks. It is the closest living relative of the extinct great auk. Historically, it has also been known as "auk", "razor-billed auk" and "lesser auk".

<span class="mw-page-title-main">Chipping sparrow</span> Species of bird

The chipping sparrow is a species of New World sparrow, a passerine bird in the family Passerellidae. It is widespread, fairly tame, and common across most of its North American range.

<i>Passerina</i> Genus of birds in the cardinal family

The genus Passerina is a group of birds in the cardinal family (Cardinalidae). Although not directly related to buntings in the family Emberizidae, they are sometimes known as the North American buntings.

<span class="mw-page-title-main">Blue-headed vireo</span> Species of bird

The blue-headed vireo is a migrating song bird found in North and Central America. There are currently two recognized subspecies that belong to the blue-headed vireo. It has a range that extends across Canada and the eastern coast of the United-States, Mexico and some of Central America. It prefers large temperate forests with a mix of evergreen trees and deciduous under growth.

<span class="mw-page-title-main">Yellow-rumped warbler</span> Species of bird

The yellow-rumped warbler is a regular North American bird species that can be commonly observed all across the continent. Its extensive distribution range connects both the Pacific and Atlantic coasts of the U.S. as well as Canada and Central America, with the population concentrating in the continent's northern parts during the breeding season and migrating southwards to southern North and Central America in Winter. The species generally prefers coniferous forests or mixed coniferous-deciduous forests as its breeding habitat, while during the winter it can be found inhabiting more open areas such as shrublands that offer food resources. The diet of the yellow-rumped warbler is based primarily on insects, though the species does eat fruits such as juniper berries as well, especially in winter.

<span class="mw-page-title-main">Grasshopper sparrow</span> Species of bird

The grasshopper sparrow is a small New World sparrow. It belongs to the genus Ammodramus, which contains three species that inhabit grasslands and prairies. Grasshopper sparrows are sometimes found in crop fields and they will readily colonize reclaimed grassland. In the core of their range, grasshopper sparrows are dependent upon large areas of grassland where they avoid trees and shrubs. They seek out heterogenous patches of prairie that contain clumps of dead grass or other vegetation where they conceal their nest, and also contain barer ground where they forage for insects, spiders, and seeds. Grasshopper sparrows are unusual among New World sparrows in that they sing two distinct song types, the prevalence of which varies with the nesting cycle. The primary male song, a high trill preceded by a stereotyped series of short chips, is reminiscent of the sounds of grasshoppers and is the origin of this species' name. Like some other birds of the central North American grasslands, this species also moves around a lot, not only via annual migrations, but individuals frequently disperse between breeding attempts or breeding seasons. Grasshopper sparrows are in steep decline across their range, even in the core of the breeding distribution in the tallgrass prairies of the central Great Plains. The Florida grasshopper sparrow is highly endangered.

<span class="mw-page-title-main">Dickcissel</span> Species of bird

The dickcissel is a small seed-eating migratory bird in the family Cardinalidae. It breeds on the prairie grasslands of the Midwestern United States and winters in Central America, northern Colombia, and northern Venezuela. It is the only member of the genus Spiza, though some sources list another supposedly extinct species.

<span class="mw-page-title-main">Little blue heron</span> Species of bird

The little blue heron is a small heron of the genus Egretta. It is a small, darkly colored heron with a two-toned bill. Juveniles are entirely white, bearing resemblance to the snowy egret. During the breeding season, adults develop different coloration on the head, legs, and feet.

<span class="mw-page-title-main">Lazuli bunting</span> Species of bird

The lazuli bunting is a North American songbird named for the gemstone lapis lazuli.

<span class="mw-page-title-main">Broad-tailed hummingbird</span> Species of bird

The broad-tailed hummingbird is a medium-sized hummingbird species found in highland regions from western United States and Western Canada to Mexico and Guatemala.

<span class="mw-page-title-main">Painted bunting</span> Species of bird native to North America

The painted bunting is a species of bird in the cardinal family, Cardinalidae. It is native to North America. The bright plumage of the male only comes in the second year of life; in the first year they can only be distinguished from the female by close inspection.

<span class="mw-page-title-main">Varied bunting</span> Species of songbird

The varied bunting is a species of songbird in the cardinal family, Cardinalidae.

<span class="mw-page-title-main">Blue grosbeak</span> Species of bird

The blue grosbeak, is a medium-sized North American passerine bird in the cardinal family Cardinalidae. It is mainly migratory, wintering in Central America and breeding in northern Mexico and the southern United States. The male is blue with two brown wing bars. The female is mainly brown with scattered blue feathers on the upperparts and two brown wing bars.

<span class="mw-page-title-main">Blue bunting</span> Species of bird

The blue bunting is a species of passerine in the family Cardinalidae, the cardinals or cardinal grosbeaks. It is found in Belize, El Salvador, Guatemala, Honduras, Mexico, and Nicaragua.

<span class="mw-page-title-main">Orange-breasted bunting</span> Species of bird

The orange-breasted bunting is a species of passerine bird in the family Cardinalidae. It is endemic to Mexico, where its natural habitats are subtropical or tropical dry forests and subtropical or tropical dry shrubland. With its wide range and large total population, the International Union for Conservation of Nature considers it as being of "least concern".

<span class="mw-page-title-main">Rose-bellied bunting</span> Species of bird

The rose-bellied bunting or Rosita's bunting is a species of bird in the family Cardinalidae, the cardinals or cardinal grosbeaks. It is endemic to a very small area of southern Mexico.

William Lay Thompson was an American ornithologist, naturalist and educator. He was Professor Emeritus of Biological Sciences at Wayne State University, an expert on bird vocalizations, past President of the Michigan Audubon Society, and past Editor of the Jack Pine Warbler.

References

  1. ↑ BirdLife International (2018). "Passerina cyanea". IUCN Red List of Threatened Species . 2018: e.T22723951A132171198. doi: 10.2305/IUCN.UK.2018-2.RLTS.T22723951A132171198.en . Retrieved 11 November 2021.
  2. ↑ "Passerina cyanea". Integrated Taxonomic Information Systems. Retrieved 2008-07-12.
  3. ↑ Whitaker, William. "Passer". Words by William Whitaker. Retrieved 2008-07-12.
  4. ↑ Payne, Robert B. (February 4, 2020). "Indigo Bunting (Passerina cyanea), version 1.0". Birds of the World. doi:10.2173/bow.indbun.01 – via birdsoftheworld.org.
  5. ↑ Sharpe, Roger S.; W. Ross Silcock; Joel G. Jorgensen (2001). Birds of Nebraska: Their Distribution and Temporal Occurrence. University of Nebraska Press. p. 430. ISBN   0-8032-4289-1.
  6. ↑ Campbell, Robert Wayne (2001). The Birds of British Columbia. UBC Press. p. 184. ISBN   0-7748-0621-4.
  7. ↑ Klicka, J; Fry AJ; Zink RM; Thompson CW (April 2001). "A Cytochrome-b Perspective on Passerina Bunting Relationships" (PDF). The Auk . 118 (3): 610–623. doi:10.1642/0004-8038(2001)118[0610:ACBPOP]2.0.CO;2. S2CID   407700 . Retrieved 14 July 2008.
  8. 1 2 Terres, J. K. (1980). The Audubon Society Encyclopedia of North American Birds . New York, NY: Knopf. pp.  290. ISBN   0-394-46651-9.
  9. 1 2 3 4 5 "Indigo Bunting". All About Birds. Cornell Lab of Ornithology. 2003. Archived from the original on 2006-04-13. Retrieved 2008-07-12.
  10. ↑ CRC Handbook of Avian Body Masses by John B. Dunning Jr. (Editor). CRC Press (1992), ISBN   978-0-8493-4258-5.
  11. ↑ Gough, Gregory (2003). "Passerina cyanea". USGS Patuxent Wildlife Research Center. Archived from the original on 2021-11-13. Retrieved 2008-07-12.
  12. ↑ "Passerina cyanea". Audubon Society. 2003. Archived from the original on 2008-06-10. Retrieved 2008-07-29.
  13. 1 2 3 4 5 Zumberg, R (1999). "Passerina cyanea". Animal Diversity Web. University of Michigan Museum of Zoology. Archived from the original on 2021-11-13. Retrieved 2008-07-12.
  14. ↑ Johnston, David W. (1967). "The Identification of Autumnal Indigo Buntings". Bird-Banding. 38 (3): 211–214. doi:10.2307/4511386. ISSN   0006-3630. JSTOR   4511386.
  15. ↑ "Indigo Bunting Overview, All About Birds, Cornell Lab of Ornithology". www.allaboutbirds.org. Archived from the original on 2021-11-13. Retrieved 2021-03-09.
  16. 1 2 Blake, Charles H. (1969). "Notes on the Indigo Bunting". Bird-Banding. 40 (2): 133–139. doi:10.2307/4511557. ISSN   0006-3630. JSTOR   4511557.
  17. ↑ Sibley, Charles Gald; Burt Leavelle Monroe (1991). Distribution and Taxonomy of Birds of the World. Yale University Press. p. 775. ISBN   0-300-04969-2.
  18. 1 2 3 4 Johnston, David W. (1965). "Ecology of the Indigo Bunting in Florida". Quarterly Journal of the Florida Academy of Sciences. 28 (2): 199–211. ISSN   0015-3850. JSTOR   24314739.
  19. 1 2 3 "Indigo Bunting (Passerina cyanea) - BirdLife species factsheet". datazone.birdlife.org. Archived from the original on 2021-11-13. Retrieved 2021-04-25.
  20. ↑ Eliott, Lang (2004). Know Your Bird Sounds. Stackpole Books. p. 23. ISBN   0-8117-2964-8.
  21. ↑ Kaufman, Kenneth (2001). Birds of North America. HMCo Field Guides. p. 366. ISBN   0-618-13219-8.
  22. 1 2 3 4 5 6 Kaufman, Kenneth (2001). Lives of North American Birds. HMCo Field Guides. p. 569. ISBN   0-618-15988-6.
  23. ↑ Emlen, Stephen T. (October 1967). "Migratory Orientation in the Indigo Bunting, Passerina cyanea – Part II: Mechanism of Celestial Orientation" (PDF). The Auk . 84 (4): 463–489. doi:10.2307/4083330. JSTOR   4083330 . Retrieved 2008-07-12.
  24. ↑ Emlen, Stephen T. (1967). "Migratory Orientation in the Indigo Bunting, Passerina cyanea: Part I: Evidence for Use of Celestial Cues". The Auk. 84 (3): 309–342. doi: 10.2307/4083084 . ISSN   0004-8038. JSTOR   4083084.
  25. ↑ Emlen, Stephen T. (1967-10-01). "Migratory Orientation in the Indigo Bunting, Passerina cyanea. Part II: Mechanism of Celestial Orientation". The Auk. 84 (4): 463–489. doi:10.2307/4083330. JSTOR   4083330.
  26. ↑ Harrison, Hal H. (2001). A Field Guide to Western Birds' Nests. HMCo Field Guides. p. 231. ISBN   0-618-16437-5.
  27. ↑ Fergus, Charles (2000). Wildlife of Pennsylvania and the Northeast. Stackpole Books. pp. 316–317. ISBN   0-8117-2899-4.
  28. ↑ Johnsgard, Paul A. (1997). The Avian Brood Parasites: Deception at the Nest. Oxford: Oxford University Press. p. 349. ISBN   0-19-511042-0.
  29. ↑ Payne, R. (1992). The Birds of North America (no 4).

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.