PASSERINE BIRDS OF NEW YORK 85 



five days from the egg, the tracts being the same as in the adult. 

 The only way to get any idea of how a moult proceeds is to appre- 

 ciate the fact that it begins almost simultaneously at a number 

 of points in the different tracts and advances independently from 

 each of them. This is why a bird seems to be moulting at 

 irregular spots all over. There is, as might be expected, a good 

 deal of individual irregularity in the growth of new feathers, but 

 when each tract is studied separately, each will be found to have 

 a definite plan of development which in its turn fits into the 

 general scheme of the process we call the moult. There is far 

 more symmetry in all this than would be imagined from the 

 study of a few specimens and the moult may well be likened to 

 a flood tide which gradually spreads over the different islands of 

 feathers found on a bird's body. It is important to note that the 

 tide of moult may pass by certain feathers which later succumb 

 to it so that a few new ones are always to be expected on the 

 body very near the points where the moult began. What is 

 more important yet, certain feathers or groups of feathers are 

 often entirely passed by and persist old and worn until another 

 period of moult. This suppression is the rule at the prenuptial 

 moult, especially in young birds and females, but rarely occurs 

 at the postnuptial period. When such feathers are of a different 

 color from those of the new plumage surrounding them, they 

 are very conspicuous, but may usually be recognized as belong- 

 ing to a previous plumage by their frayed and faded appearance. 

 Young birds are most apt to fail to renew these stray feathers, 

 often whole patches of them, particularly when the adult plum- 

 age is brilliantly colored, as for instance, in the Indigo Bunting 

 [Passcriiia cyancd) or Orchard Oriole (^Icterus spurius). It 

 would seem that the tide of moult fails to rise or exhausts itself 

 sooner in the young bird than in the adult, consequently the 

 young of some species pass their first breeding season in a 

 plumage adorned with only a few new feathers colored like 

 those of the adult. This is true of the species just mentioned, 

 and the Redstart {Sctophaga riiticilla) and Summer Tanager 

 {PlriDiga nibra), are also other good examples. When only a 

 few new feathers are assumed they are confined chiefl)' to the 



