PASSERINE BIRDS OF NEW YORK 241 



MNIOTILTID.E 



Many of our Warblers undergo a semi-annual moult which 

 is often extensive at the time of the prenuptial moult. 5. ruticilla 

 is perhaps unique among them in having a limited first prenuptial 

 moult which is apparently not repeated, although I suspect a 

 similar peculiarity may be found to prevail among several others. 

 The prenuptial period of moult seems to be a protracted one, be- 

 ginning even in November and extending into May. As most 

 of the species are in the tropics at this time we do not know 

 much about the changes in plumage except as we may judge 

 from somewhat worn specimens when they reach us in the 

 spring, and from a few extra-limital specimens. The types of 

 moult are numerous in this large family, but with one possible 

 exception (Ictcria virens) the remiges and rectrices are retained 

 until the first postnuptial moult. The renewal at the prenuptial 

 moult varies greatly in amount and when confined to a few 

 feathers of the head and chin is very difficult to determine. As 

 a ,rule adult winter plumages and adult nuptial plumages are not 

 very different. The Juvenal plumage is quickly replaced by the 

 first winter which is apt to resemble closely the female adult 

 winter dress. In many species the first prenuptial moult renders 

 old and young practically indistinguishable although such feath- 

 ers of the old plumage as remain throw much light upon the 

 age of doubtful specimens. Great confusion has existed as to 

 the first winter or " immature " plumage of many species and 

 still less has been known of the adult winter dress. 



Mniotilta varia (Linn.). BLACK AND WHITE WARBLER 



1. NATAL DOWN. Mouse-gray. 



2. JUVENAL PLUMAGE acquired by a complete postnatal moult. 



Above, wood-brown streaked with dull olive-brown, the upper tail coverts dusky ; 

 median crown and superciliary stripe dingy white. Wings and tail dull black, 

 edged chiefly with ashy gray, the tertiaries (except the proximal which is 

 entirely black) broadly edged with white, buff tinged on the middle one Two 

 buffy white wing bands at tips of greater and median wing coverts. The outer 

 two rectrices with terminal white blotches of variable extent on the inner webs. 

 ANNALS N. Y. ACAD. Sci., XIII, Oct. 17, 1900 16. 



