PASSERINE BIRDS OF NEW YORK 93 



2. Humeral or Shoulder Tracts [PtcrylcB Jiuincrales). A tol- 

 erably symmetrical, bilateral outbreak of new feathers takes 

 place very early in this pair of tracts showing usually at the 

 median and internal portion. The moult proceeds forwards, 

 seemingly effecting a junction with the lateral branches of the 

 ventral tract near the edges of the wing membranes at the 

 very time the moult in them has reached this point ; and back- 

 wards to the posterior margin of the upper arm joining very 

 nearly the humeral coverts. Old feathers frequently persist at 

 these junction points and also externally, particularly in young 

 birds. These tracts follow the example of the body plumage 

 in their moult, and not that of the alar tract, being renewed in 

 many species twice a year. 



3. Capital or Head Tract {Pteryla capitis). The pterylog- 

 raphy of this important tract requires a little more explanation 

 than is usually given it in order to understand its moult. Al- 

 though the head is practically entirely covered (save a small 

 spot behind the eye) with a multitude of extremely small 

 feathers in Passerine species, they are arranged in several 

 groups or series. Starting at the nostrils near the base of 

 the upper mandible two rather broad bands pass backward 

 over the crown, but before reaching the occiput they widen 

 out curving laterally to the postauricular region, the lines of 

 feathers on the occiput extending laterally. On each side of 

 the head is a narrow band corresponding to the superciliary 

 stripe ; another includes the loral and circumocular region ; 

 another passes from the gape backward in a loop includ- 

 ing the auriculars ; and finally there is a submalar band starting 

 beneath the middle of the ramus of the lower mandible and 

 joining the auriculars at a point near where they are joined by 

 the short auricular branch of the ventral tract. There seems 

 to be some relation between these mmor tracts and the distri- 

 bution of color ; and moult begins independently in any or all 

 of them at about the same time and, as a rule, tends to proceed 

 from before backwards. The auriculars being the largest areas 

 are usually the first and often the last to show moult. A fre- 

 quent point of departure is just back of the extreme anterior 



