Plumages, Molts, and Structure

The Green Jay has 10 primaries (numbered distally, from innermost p1 to outermost p10, with the outermost reduced in length), 9 secondaries (numbered proximally, from outermost s1 to innermost s9, and including 3 tertials, s7–s9 in passerines), and 12 rectrices (numbered distally, from innermost r1 to outermost r6 on each side of the tail). Geographic variation in appearance is moderate; the following molt and plumage descriptions pertain to the northern subspecies, luxuosus; see Systematics: Subspecies for appearance variation in other recognized subspecies. No geographic or sex-specific variation in molt strategies have been reported, although timing may vary with latitude in Mexico and Central America responding to variable timing of breeding, daylight regimes, and environmental factors.

See Molts for molt and plumage terminology. The following is based primarily on detailed plumage descriptions of Ridgway (11 Ridgway, R. (1904). The Birds of North and Middle America Part III. Bulletin of the United States National Museum 50. Close ), Oberholser (12 Oberholser, H. C. (1974). The Bird Life of Texas. University of Texas Press, Austin, Texas, USA. Close ), and Goodwin (13 Goodwin, D. (1976). Crows of the World. Comstock Publishing Associates, Ithaca, New York, USA. Close ); see Pyle (14 Pyle, P. (1997). Identification Guide to North American Birds. Part I. Slate Creek Press, Bolinas, CA, USA. Close , 15 Pyle, P. (2022). Identification Guide to North American Birds. Part I, Second Edition. Slate Creek Press, Forest Knolls, CA, USA. Close ) for age-related criteria. Sexes show similar appearances in all plumages. Definitive Plumage is assumed following Second Prebasic Molt.

Natal Down

Present primarily in April–June in North America, in the nest. Hatching chicks are “very dark skinned and quite naked” (16 Roles, D. G. (1971). The breeding Mexican Green Jay at the Jersey Zoological Park. Avicultural Magazine 77:20–22. Close ). In four-day-old Texas birds, the head and spinal tracts are greenish gray; primary and secondary quills begin to sprout and are dull bluish (17 Friedmann, H. (1925). Notes on the birds observed in the lower Rio Grande Valley of Texas during May 1924. Auk 42(4):538–548. Close ). In Colombia, chicks have emerging feather sheaths lining well-marked tracts of feathers by day 7 (8 Alvarez, H. (1975). The social system of the Green Jay in Colombia. Living Bird 14:5–44. Close ).

Juvenile (First Basic) Plumage

Present primarily May–July in North America. Similar to later plumages, but head and nasal tufts are dull bluish washed brown; lower auriculars and hindneck pale blue to blue-green; subocular and superciliary spot paler; black on sides of head, chin, and throat washed brown; wing coverts dull greenish washed brown; underparts pale yellow. Juvenile primaries and rectrices are narrower and more tapered (less truncate) at the tips than definitive basic feathers. Body feathering (especially undertail coverts) is more filamentous due to lower barb densities.

Formative Plumage

"First Basic" or "Basic I" plumage of Humphrey and Parkes (18 Humphrey, P. S., and K. C. Parkes (1959). An approach to the study of molts and plumages. The Auk 76(1):1–31. Close ) and some subsequent authors; see revision by Howell et al. (19 Howell, S. N. G., C. Corben, P. Pyle, and D. I. Rogers (2003). The first basic problem: a review of molt and plumage homologies. Condor 105:635–653. Close ). Present primarily August–July in North American populations. Similar to Definitive Basic Plumage except retained juvenile primary coverts and occasionally some greater coverts are relatively worn and brownish, contrasting with replaced formative greater coverts; retained juvenile outer rectrices and outer primaries are relatively worn, narrow, and tapered at the tips versus broader and truncate in Definitive Basic Plumage, the primaries washed brownish; sometimes 1–2 or more central rectrices can be replaced and contrastingly fresh.

Definitive Basic Plumage

Present primarily August–July. Nasal and frontal plumes are stiffened and semi-erect but very short and not forming a crest, deep blue; forehead and postocular spot white to bluish-white; crown, nape, and lower auricular patch deep blue or blue with minimal white mottling. Lores, sides of head (other than postocular spot and lower auricular patch), sides of neck, chin, throat, and upper breast are black. Nape, back, rump, uppertail coverts, upperwing coverts, and edging to remiges are green, sometimes slightly tinged blue, the nape sometimes brighter green where it meets the blue of the hindcrown; central two pairs of rectrices (r1–r2) are dark green becoming greenish-blue at the tip from above and blackish from below; the outer three pairs of rectrices are bright yellow. Central breast and remaining underparts are greenish to yellow-green, often greener on the sides and flanks and brighter yellow ventrally to the undertail coverts and femoral feathering. Bases to outer webs of remiges from below and underwing coverts are yellow.

Definitive Basic Plumage is separated from Formative Plumage by having upperwing secondary coverts, primary coverts, tertials, and secondaries uniformly green, without molt limits; basic rectrices and outer primaries are darker (blackish on inner webs), glossier, broader, and with truncated tips.

South American populations are somewhat larger. The nasal and frontal plumes are longer, stiffened, and erect, forming a bushy crest. South American populations also tend to be less greenish and yellowish, with more blue-green and creamy white than northern population (13 Goodwin, D. (1976). Crows of the World. Comstock Publishing Associates, Ithaca, New York, USA. Close ; see Subspecies).

Molt and plumage terminology follows Humphrey and Parkes (18 Humphrey, P. S., and K. C. Parkes (1959). An approach to the study of molts and plumages. The Auk 76(1):1–31. Close ) as modified by Howell et al. (19 Howell, S. N. G., C. Corben, P. Pyle, and D. I. Rogers (2003). The first basic problem: a review of molt and plumage homologies. Condor 105:635–653. Close ). The Green Jay exhibits a Complex Basic Strategy (cf. 19 Howell, S. N. G., C. Corben, P. Pyle, and D. I. Rogers (2003). The first basic problem: a review of molt and plumage homologies. Condor 105:635–653. Close , 20 Howell, S. N. G. (2010). Peterson Reference Guide to Molt in North American Birds. Houghton Mifflin Harcourt, Boston, Massachusetts, USA. Close ), including complete prebasic molts and a partial preformative molt but no prealternate molts (21 Bent, A. C. (1946). Life histories of North American jays, crows, and titmice, Part 2. United States National Museum Bulletin 191. Close , 12 Oberholser, H. C. (1974). The Bird Life of Texas. University of Texas Press, Austin, Texas, USA. Close , 22 Pyle, P. (1997). Molt limits in North American passerines. North American Bird Bander 22:49–89. Close , 14 Pyle, P. (1997). Identification Guide to North American Birds. Part I. Slate Creek Press, Bolinas, CA, USA. Close , 15 Pyle, P. (2022). Identification Guide to North American Birds. Part I, Second Edition. Slate Creek Press, Forest Knolls, CA, USA. Close ; Figure 1).

Prejuvenile (First Prebasic) Molt

Complete, primarily April–June, in the nest. Hatchings are “very dark skinned and quite naked” (16 Roles, D. G. (1971). The breeding Mexican Green Jay at the Jersey Zoological Park. Avicultural Magazine 77:20–22. Close ). In four-day-old Texas birds, head and spinal tracts are greenish-gray; primary and secondary quills begin to sprout and are dull bluish (17 Friedmann, H. (1925). Notes on the birds observed in the lower Rio Grande Valley of Texas during May 1924. Auk 42(4):538–548. Close ). In Colombia, chicks have emerging feather sheaths lining well-marked tracts of feathers by day 7 (8 Alvarez, H. (1975). The social system of the Green Jay in Colombia. Living Bird 14:5–44. Close ). Juvenile plumage is acquired during a period of 14–15 d following hatching; molt presumably complete or near-complete by fledging at days 16–18.

Preformative Molt

"First Prebasic" or "Prebasic I" molt of Humphrey and Parkes (18 Humphrey, P. S., and K. C. Parkes (1959). An approach to the study of molts and plumages. The Auk 76(1):1–31. Close ) and some subsequent authors; see revision by Howell et al. (19 Howell, S. N. G., C. Corben, P. Pyle, and D. I. Rogers (2003). The first basic problem: a review of molt and plumage homologies. Condor 105:635–653. Close ). Partial, primarily June–September, on or near natal territory. Includes most or all body plumage and upperwing secondary coverts (occasionally up to most outer greater coverts and 1–2 outer median coverts can be retained), usually 1–3 tertials, and sometimes 1–2 central rectrices (rarely more), but no primary coverts, primaries, or outer secondaries or rectrices (22 Pyle, P. (1997). Molt limits in North American passerines. North American Bird Bander 22:49–89. Close , 15 Pyle, P. (2022). Identification Guide to North American Birds. Part I, Second Edition. Slate Creek Press, Forest Knolls, CA, USA. Close ).

Definitive Prebasic Molt

Complete, primarily June–September, on breeding territory. Can begin as early as May in non-breeding yearlings due to lack of breeding constraints. Primaries are replaced distally, from innermost p1 to outermost p10, secondaries replaced bilaterally from the central tertial (s8) and proximally from outermost s1, and rectrices replaced distally, from innermost r1 to outermost r6, on each side of tail, with some variation in sequence possible. Reports of secondaries being replaced distally (e.g., 14 Pyle, P. (1997). Identification Guide to North American Birds. Part I. Slate Creek Press, Bolinas, CA, USA. Close ) appear to be in error.

Bill

The bill is black. Nestlings have a lighter black bill. The roof of the mouth is white at hatching and becomes completely black at around one year of age (14 Pyle, P. (1997). Identification Guide to North American Birds. Part I. Slate Creek Press, Bolinas, CA, USA. Close ).

Iris

The iris is brown in Texas, northeastern Mexico, and western Mexico birds. The iris is yellow throughout the rest of geographic range.

Tarsi and Toes

Tarsi and toes are black.

Linear Measurements

The vast majority of morphological data come from southern Texas (12 Oberholser, H. C. (1974). The Bird Life of Texas. University of Texas Press, Austin, Texas, USA. Close ; A. Arredondo, unpublished data; M. Conway, unpublished data). In adult birds, the overall length ranges from 26 to 32 cm; total wingspan averages 34.3 cm. Wing chord ranges from 113 to 122 mm in males and 110 to 118 mm in females. Exposed culmen averages 24.9 mm in adult males and 24.4 mm in adult females. Tail length averages 126.0 mm in males and 127.5 mm in females. Tarsus length averages 37.6 mm in both males and females, and middle toe length without nail averages 21.1 mm in males and 20.1 mm in females.

Some measurements are available of 72 hatch-year birds in southern Texas (M. Conway, unpublished data). Wing chord averaged 115.9 mm (107–124 mm), and tail length averaged 125.7 mm (100.0–137.0 mm).

Mass

In southern Texas, adult females average 77.8 g (68.5–89.0 g) and adult birds of unknown sex average 75.8 g (63.0–92.2; 23 Gayou, D. C. (1985). Body weights of south Texas Green Jays (Cyanocorax yncas). Bulletin of the Texas Ornithological Society 18:30–31. Close ; M. Conway, unpublished data). On the northeastern edge of the range near Sinton, Texas, an adult male and adult female were 82.5 and 77.5 g, respectfully (A. Arredondo, unpublished data). Hatch-year birds average 72.0 g (57.0–86.0 g; M. Conway, unpublished data).

Little data on mass in other parts of the range, but birds are heavier to the south, including an average adult mass of 99.7 g in Mexico (70.6–125.0 g; 6 Dunning, J. B., Jr. (1984). Body weights of 686 species of North American birds. Western Bird Banding Association Monograph No. 1. Eldon Publishing, Cave Creek, AZ, USA. Close ). Nine jays measured in northeastern Mexico averaged 112.0 g (24 Gayou, D. C. (1995). Green Jay (Cyanocorax yncas). In The Birds of North America, No. 187 (A. Poole and F. Gill, Editors), Academy of Natural Sciences, Philadelphia, and The American Ornithologists' Union, Washington, DC, USA. Close ).