Appearance

Orange-breasted Bunting is a very distinctive species. The adult male is basically unmistakeable, with its bright yellow underparts and spectacles, orange breast band, turquoise upperparts, and green crown. Females and immatures are entirely green above, with yellow lores and yellow underparts. The song of Orange-breasted Bunting is slower than other buntings, although the calls are similar to those of other species. There are two subspecies of Orange-breasted Bunting, but these differ only in size.

Male Orange-breasted Bunting is unmistakable. Females and immatures are similar to comparable plumages of Painted Bunting (Passerina ciris), but the latter has a narrow pale eyering with green (not yellow) lores, often is brighter and greener overall, and has green, not turquoise, uppertail coverts (Howell and Webb 1995).

This description is based on Ridgway (1901) and on Howell and Webb (1995):

Adult male: Crown yellow green or apple green crown. Rest of upperparts electric turquoise blue, back usually tinged with green. Lores, eyering, and underparts are lemon (or canary) yellow, deepening into cadmium yellow or golden orange on the chest.

Adult female: Upperparts grayish green, becoming bluish on the auriculars, wings, uppertail coverts, and tail. Lores, eyering, throat, and underparts are yellow, shaded with gray along the sides and chest.

Immature male: Similar to adult female but brighter, with more turquoise on the auriculars and uppertail coverts, as well as more orange on the chest.

Immature female: Similar to adult female, but head and upperparts grayee, with little or no turquoise. The chest is duskier and the yellow underparts duller.

Juvenile: Resembles a dull immature female but with a streaked chest (Howell and Webb 1995).

The Orange-breasted Bunting shows the same molt sequence as others of its genus, with juvenile, formative, basic and alternate plumages (Thompson and Leu 1995). However, a unique characteristic of their molting sequence (shared only with the Rose-bellied Bunting Passerina rositae) is that both sexes show delayed plumage maturation, where younger birds molt into dull plumages despite being mature enough to reproduce. This is relatively common in male birds, but uncommon in females. This bird also has the brightest-colored females of any Passerina or Cyanocompsa bunting, which may serve as an honest status signal (Thompson and Leu 1995). Like the Lazuli (Passerina amoena)and Indigo (Passerina cyanea) buntings, males grow adult-like, albeit duller, plumage in the first prebasic and prealternate molts, unlike Painted (Passerina ciris) and Varied (Passerina versicolor) buntings, which grow female-like feathers in these molts. Similar to the latter two and unlike the former, however, subadult male Orange-breasted Bunting have a limited first prealternate molt that leaves its plumage identical between winter and spring. Neither the Painted Bunting nor the Orange-breasted Bunting show color differences between seasons (Thompson and Leu 1995).

The juvenile plumage is uniformly drab and brown, with dusky streaking (Thompson and Leu 1995, Howell and Webb 1995). Sexes are indistinguishable (Thompson and Leu 1995).

In the preformative molt, birds replace all body plumage but the greater primary and secondary coverts. The molt begins when the juvenal flight feathers are still growing a few days after fledging in early June to late September (Thompson and Leu 1995).
The formative plumage is the first that shows delayed plumage maturation. The males have a dull breast band while females retain olive streaks in their yellow underparts. Birds retain all juvenal greater secondary coverts, which are brown, and all juvenal flight feathers (Thompson and Leu 1995).

During the first prebasic molt, the Orange-breasted Bunting changes all its body plumage, rectrices, outer six primaries, and inner four secondaries, excepting some greater primary coverts. This molt overlaps with the end of the preformative molt in August in September, but differs in resulting feather colors and replaces body feathers that were also changed in earlier molts. The prebasic molt occurs from August through December, taking around 50 days and peaking in September (Thompson and Leu 1995).

The new flight feathers are distinctive in the first basic plumage, which are darker than the juvenal feathers. Both sexes continue showing delayed plumage maturation, although they are brighter than in the formative plumage. Males are similar to adult females but have blue auriculars, an orange breast band, and a green crown and back. Females have a yellow chin a nd throat (Thompson and Leu 1995).

The first prealternate molt is restricted to some head and body feathers and may be skipped entirely in some birds. It is more intense in females than in males and occurs from March through May (Thompson and Leu 1995).

The first alternate plumage still displays some delayed plumage maturation, but the females no longer show olive streaking and the males have blue tips to their mantle feathers, concealing the green bases. It is only slightly less colorful than that of adult birds (Thompson and Leu 1995).

The definitive prebasic molt replaces all body plumage, which is usually very worn due to their abrasive habitat. It begins with the innermost primary (P1) and the tertials (S8), with most secondaries molting while P3, 4, or 5 is dropped, beginning with S1. All juvenile greater wing coverts are replaced with blue-edged ones. The molt occurs from July through November, although some younger birds can begin molting a month early (Thompson and Leu 1995).

The buntings show complete maturation in the definitive basic plumage, where the males have green tipped mantle feathers that wear into their blue bases, a broad orange breast band, and cerulean blue upperparts, while all greater primary coverts and remiges (excepting P9) have a blue edging (Thompson and Leu 1995).
The definitive prealternate molt is a limited molt occurring in March, April and May that replaces body feathers of any region (not including flight feathers). It is very difficult to determine because its resulting plumage is identical to the definitive basic plumage (Thompson and Leu 1995).

Iris: dark brown

Bill: blackish gray, base of mandible grayer

Tarsi and toes: grayish

Bare parts color data from Brewer (2011).

Total length: 11.5-12.5 cm (Howell and Webb 1995). 11.7-13.9 cm (Ridgway 1901)

Linear measurements of adult male (n = 12, specimens, combined sample of leclancherii and grandior; Ridgway 1901):

wing length: mean 68.33 mm, range 65.28-73.15 mm

tail length: mean 53.09 mm, range 48.77-57.91 mm

bill length (exposed culmen): mean 11.8 mm, range 10.67-11.68 mm

bill depth at base (n = 3): 7.62-7.87 mm

tarsus length: mean 17.02 mm, range 16.26-17.78 mm

middle toe length: mean 11.94 mm, range 11.48-12.45 mm

Linear measurements of adult female (n = 5, specimens, combined sample of leclancherii and grandior; Ridgway 1901):

wing length: mean 64.01 mm, range 60.71-66.04 mm

tail length: mean 48.51 mm, range 44.20-49.78 mm

bill length (exposed culmen): mean 11.18 mm, range 10.67-11.43 mm

bill depth at base: mean 7.78 mm, range 7.62-7.87 mm

tarsus length: mean 17.02 mm, range 16.26-17.53 mm

middle toe length: mean 11.68 mm, range 11.18-12.19 mm

The two subspecies of Orange-breasted Bunting differ mainly in size (Griscom 1934). The wing of male leclancherii measure 64-66 mm (mean 65.2 mm) and the wing of the female measure 60-61 mm (mean 60.5 mm). The wings of male grandior measure 67.5-70.3 mm (mean 68.8mm) and of females measure 63-64.5 mm (mean 63.9 mm; Griscom 1934).

Mass: mean 14.5 g (range 12-15.1 g, n = 7, sexes combined; Dunning 2008).