f'liiiihigc of the Yucafan Jay. 113 



beak and white-tipped rectrices as " immature " characters. 

 ''/his he evidently bases on Chapman (3) whose notes on this 

 species are obtained at first hand in the field. Cliapman writes 

 as follows : 



" Current descriptions of this bird, including that in the 

 ' Biologia.' ascribe the differences shown by certain individuals 

 in the colour of the bill and tail to sex. the male being stated 

 <o have a black bill and tail, while the female is said to have 

 the bill yellow and the tail tipped with white. My series of 

 twelve specimens shows that this variation is not sexual, but is 

 evidently due to age. Thus I have males and females with 

 black bills and tails, and also examples of both sexes in which 

 the bill is yellow and the tail tipped with white. The series 

 also contains intermediates between the two extremes. 



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 

 individuals, about one in every four birds giving evidence of 

 immaturity." 



The chief points of interest may be thus summed up : 



1. The Juvenal plumage of CissUopho yucatanica 'S 

 characterized chiefly by the entire head, neck and under parts 

 being wliite : 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 wnnter 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 underparts become black; the iris darkens to a cold slaty 

 gray; the primaries and rectrices 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 

 complete in the body plumage of head, neck and underparts in 

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



3—1896. Chapman, Bull. Amer. Mus. Nat. His., VIII., 282. 

 5— 190n, Dwight, Ann. N. Y. Acad. Sci., XIII., 152, 



