Identification

The Green Jay is similar in size to other jays, with a stout body and broad, rounded wings. Total length ranges from 26 to 32 cm; wingspan 34.3 cm (1 Meyer de Schauensee, R., and W. H. Phelps (1978). A Guide to the Birds of Venezuela. Princeton University Press, Princeton, NJ, USA. Close , 2 Howell, S. N. G., and S. Webb (1995). A Guide to the Birds of Mexico and Northern Central America. Oxford University Press, New York, NY, USA. Close , 3 Hilty, S. L., and W. L. Brown (1986). A Guide to the Birds of Colombia. Princeton University Press, Princeton, NJ, USA. Close , 4 Sibley, D. A. (2014). The Sibley Guide to Birds, second edition. Alfred A. Knopf, New York, NY, USA. Close ). In southern Texas, the mass of adult birds is about 80 g (5 Gayou, D. C. (1985). The behavioral ecology of Texas Green Jays (Cyanocorax yncas). Ph.D. thesis, University of Missouri, Columbia, Columbia, Missouri, USA. Close ). There is 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 (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 ).

The Green Jay is visually-striking in color. Adults are pale yellow and green with a black and blue head. The face, throat, and breast are black with blue supraocular and subocular patches; the crown and nape are blue. The upperparts, wings, and tail are bright green. Yellow outer tail feathers are more noticeable when the tail is spread in flight. In flight, wings are wide and rounded.

South American birds have a whiter crown and nape, and a blue frontal crest at the base of the bill, which is lacking in other parts of the geographic range. Additionally, South American, Central American, and most Mexican birds have yellow eyes, while birds in southern Texas, and western and northeastern Mexico have dark brown eyes.

The Green Jay is unique in appearance and easily distinguishable from other jays. Genetic research (7 Bonaccorso, E., A. T. Peterson, A. G. Navarro-Sigüenza, and R. C. Fleischer (2010). Molecular systematics and evolution of the Cyanocorax jays. Molecular Phylogenetics and Evolution 54(3):897–909. Close ), along with known differences in appearance, habitat preferences (8 Alvarez, H. (1975). The social system of the Green Jay in Colombia. Living Bird 14:5–44. Close , 9 Gayou, D. C. (1986). The social system of the Texas Green Jay. Auk 103(3):540-547. Close ), and vocal behavior of South American birds may suggest future splitting into northern and southern species. A proposal to split the species into Cyanocorax yncas and Cyanocorax luxuosus was reviewed by the American Ornithological Society in 2023, but did not pass (10 Chesser, R. T., S. M. Billerman, K. J. Burns, C. Cicero, J. L. Dunn, B. E. Hernández-Baños, R. A. Jiménez, A. W. Kratter, N. A. Mason, P. C. Rasmussen, J. V. Remsen, Jr., and K. Winker (2023). Sixty-fourth Supplement to the American Ornithological Society’s Check-list of North American Birds. Ornithology 140:1–11. Close ). If split, differences in head coloration and the presence of a frontal crest would distinguish the two species in appearance (see Systematics: Subspecies).