NO. 2276. REVISION OF SAUROPATIS CHL0RI8—0BERU0LSER. 353 



are separated by water barriers from their nearest relatives, are 

 bridged by individual variation so completely that notwithstanding 

 the attempt of some authors to maintain several distinct species, it 

 is quite certain that all of the recognizable forms are but subspecies 

 of Sauropatis chloris. Furthermore, probably none of the races are 

 migratory, so that the supposed occurrences of one race within the 

 range of another are to be explained by intergradation or individual 

 variation. 



In most cases the females are distinguishable from the males by 

 duller, more greenish upper parts, more extensively blackish auri- 

 culars, and sometimes lack of bujff on the sides and flanks ; but there 

 appears to be more difference in some races than in others. There 

 are in some cases other characteristics of the female, though no diifer- 

 ence of size, so far as we have been able to discover. 



The Juvenal plumage differs from that of the adult in having the 

 pileum more brownish; remaining upper parts duller and more 

 greenish and more or less tinged with brownish ; black nuchal band 

 often more conspicuous; back just below the white cervical collar 

 more or less blackish ; tail and wings duller, less bluish (more green- 

 ish or brownish) ; white cervical collar more buffy, and its feathers 

 edged with dusky; supraloral spot more buffy; ear-coverts more 

 blackish (less greenish) ; and breast feathers margined with dusky. 



Immature birds of the first winter, as compared with adults, are 

 duller and more brownish or greenish on the upper surface, like the 

 adult female, but even darker, though more like the adult than is 

 the Juvenal plumage, and have the feathers of the breast, the white 

 cervical collar, the sides of neck and of body slightly edged with 

 dusky; also the feathers of the forehead margined with buffy white. 

 The greenish shade of the upper surface persists after other imma- 

 ture features have disappeared, so that very bluish birds are appa- 

 rently old individuals. Adult birds in worn plumage are likewise 

 decidedly more bluish above than when in fresh condition, though this 

 does not seem materially to affect the wing-quills; have the black 

 nuchal band broader, loss washed with greenish, and the ear-coverts 

 more blackish. On the other hand, freshly molted adults have often, 

 if not always, a few slight duslcy tips on the lower parts and on the 

 white cervical collar. These soon wear off, however, leaving the parts 

 pure white or buffy as the case may be. 



The molt of the juvenal plumage into that of the first winter 

 takes place between the first of September and the middle of Janu- 

 ary, chiefly during October and November. Apparently, however, 

 the full adult dress ffc not acquired until the bird is at least a year 

 and a quarter old, possibly even more. The adult molts but once a 

 year, between the middle of September and the middle of January. 

 62055— 20— Proc.N.M.vol.55 24 



