This jay has three distinct plumages, but can be successfully aged until the fourth year from changes in the eye ring and internal coloration of the upper bill. Juvenal birds are white and blue-gray, with a first prebasic molt which does not exchange the rectrices or remiges, causing the black and blue first year birds to appear adult except for the white tips of the tail feathers. The black and blue definitive adult plumage is gained in second year birds. It appears very similar to the San Blas Jay Cyanocorax sanblasianus and the Purplish-backed Jay Cyanocorax beecheii.
The Yucatan Jay looks somewhat like the Purplish-Backed Jay, Cyanocorax beecheii, but does not have a yellow iris (Davis 1957). Also appears similar to the San Blas Jay, Cyanocorax sanblasianus and the Bushy-crested Jay Cyanocorax melanocyaneus. However, the ranges of these species are not close to that of the Yucatan Jay.
Adult coloration appears in birds with second year plumage. Sexes are identical in appearance. The head, neck and underside are uniformly black. The undertail coverts are a dusky blue. The upper parts, except for the crown and hindneck, are either bright cerulean or deep turquoise blue. The tail is a deeper blue color, nearly cobalt, and the tertials have a greenish tint (Ridgway 1904).
First year birds have a deep black head and body. The mantle is blue with glaucous overtones which vary between the two subspecies. The upper wing surfaces are blue and those of the tail purplish blue. Ventrally, the wings and tail are deep gray. All of the rectrices except for the middle pair are white-tipped. These rectrices are retained from the juvenal plumage and the white tips may wear away before the second prebasic molt (Hardy 1973).
Juvenile birds have a white head and body, with the remainder of dorsal surfaces a grayish-blue color. The ventral surfaces of the wings and tail are a dull gray. The rectrices, except for the middle pair, are tipped with white (Hardy 1973).
The jays leave the nest in a juvenal plumage. The first prebasic molt involves only the body and head feathers. The resulting first basic plumage thus retains the distinctive white tips on the rectrices of the juvenal. Prior to or accompanying the first prebasic molt, the yellow pigmentation of the tarsi, toes and eyering increases.
The second prebasic molt leads to a replacement of all feathers for the definitive adult plumage.
(Source: Hardy 1973)
The Yucatan Jay has distinctive differences between age groups in the colors of the bill and tarsus. The iris appears to remain a dark black-brown throughout the age groups.
Fourth year and older birds have black bills externally. Internally, the maxilla may have varying amounts of white. Eye ring is entirely black. Tarsi and toes yellow.
Third year birds may have a small amount of yellow on the exterior of the bill, but it is mostly black. Internally, the maxilla starts out at the beginning of the year with several black spots of pigment which later join to become over 50% black. The eye ring may have a small amount of yellow until November of the third year, but is entirely black by January. Tarsi and toes yellow.
Second year birds have highly variable bills that start out almost entirely yellow and change to black and yellow bicolored by March. By the end of the second year, some individuals have very black bills, while other retain bicolored bills. The interior of the bill is white. The yellow eye ring begins to show black spots at any time during the second year and by the time of the third prebasic molt the ring becomes almost completely black with minor small yellow spots. The blackening of bill and eye ring often is not bilaterally symmetrical. The tarsi and toes of the second year bird are yellow, as in the rest of the plumages.
First year jays have yellow bill, tarsi and toes. By June or August, dark shadowing may appear on the bill, but no actual black pigment appears until September. Then, the black pigment usually appears at the nasal openings and rami of the lower mandible. The inside of the mouth is white.
Juvenile jays have bill, tarsi and toes of a pale yellow coloration with pink flesh tones. Inside of bill white. Iris dark blackish-brown.
(Above taken from Hardy 1973)
All measurements are in mm, averages for measurements are in parentheses.
|Length||310.5-326.5 (320.5)||317.5-330 (320.5)|
|Wing||137-147.5 (141)||137-143 (139.5)|
|Tail ||134.5-150 (142.5)||134.5-148.5 (141.5)|
|Bill from Nares||21-23 (22.5)||21.5-23 (22.5)|
|Depth of Bill at Nares||12-13 (12.7)||12.5-13 (12.7)|
|Tarsus||39.5-42 (41)||39.5-42 (41)|
|Middle Toe||24-25.5 (25)||24-25.5 (25)|