154 Zoologica: N. Y. Zoological Society. [I; 7 



"How long a time is required for the acquisition of the 

 adult plumage remains to be determined. Apparently at least 

 two years, for each group of jays had several yellow-billed indi- 

 viduals, about one in every four birds giving evidence of im- 

 maturity." 



The chief points of interest may be thus summed up : 



1. The Juvenal plumage of Cissilopha yucatanica is charac- 

 terized chiefly by the entire head, neck and under parts being 

 white; bill and eye-ring orange yellow; iris pale hazel brown; 

 all but the central rectrices more or less tipped with white. This 

 white plumage is retained from the time of leaving the nest, 

 about July 15th, until October. 



2. The first winter plumage is acquired exactly as in our 

 northern Cyanocitta cristata by a partial postjuvenal moult 

 (Dwight [5]), reaching its height in October. The head, neck 

 and under parts become black; the iris darkens to a cold slaty 

 gray; the primaries and rectri<;es are not moulted, but if the 

 latter are accidentally pulled out, they are replaced with feathers 

 showing no trace of white. 



3. The advance toward an adult plumage in this species is 

 marked chiefly by an increase in dark pigment ; sudden and com- 

 plete in the body plumage of head, neck and under parts in the 

 fall moult, and in the lateral rectrices in the first moult of the 

 following year ; more gradual in the color of the iris ; and still 

 more gradual in the color of the mandibles and eye-ring. 



11. 



JUVENAL PLUMAGE OF THREE INDIVIDUALS. 



Individual A. — (Fig. 51.) 



Seven Weeks Old (September 8, 1911). 



Head, neck, breast, belly and under tail-coverts pale creamy 

 white, faintly tinged on the crown with blue, all of the white 

 feathers with sooty black bases ; above, pale blue, with a few new 

 feathers of brighter blue; wing-coverts like the back; remiges 



5_1900. Dwight, Ann. N. Y. Acad. Sci., XIII, 152. 



