PASSERINE BIRDS OF NEW YORK 131 



annual renewal of plumage. With those of annual renewal, 

 however, we must go back to the postjuvenal moult which im- 

 poses upon species characters that they retain for a twelve- 

 month. But here again there is no sharp dividing line, and 

 without large series of specimens to eliminate individual varia- 

 tions, it is extremely easy to classify wrongly. For instance 

 the Horned Lark (Otocoris alpestris) would seem to belong to 

 Group A, and yet many late winter specimens show new growth 

 of a few feathers about the chin and the eyes, suggesting the 

 transference of this species to Group J. In another species, the 

 Snowflake (Plectrophenax nivalis), the regular and more exten- 

 sive growth of feathers in the same regions has led me to place 

 it, with some hesitation, in Group J, because a like extent of 

 renewal in the Lapland Longspur {Calcarius lapponicus) pro- 

 duces visible changes that in the Snowflake are not apparent. 



It is possible that when we know more of the birds classed 

 under E and F, both these groups may prove superfluous and 

 the species turn out to moult to an extremely limited extent 

 every year, but I hardly think so. They now contain birds that 

 in some individuals at least accomplish by moult at the post- 

 juvenal period what is delayed in others until the prenuptial. 



The groups I propose are fairly distinct for the majority of 

 the species included in them although there are some birds that 

 vary so in the extent of their moult as to properly belong to 

 several For example, there may be enough difference in two 

 male White-throated Sparrows (Zonotrichia albicollis) to warrant 

 placing one in Group I and the other in J, while of two females 

 one might be placed in J and the other in C. 



In species that undergo a prenuptial moult there may be 

 found every gradation from birds that renew the whole of their 

 plumage to those that merely gain a few feathers about the an- 

 terior parts of the head. It is even probable that some of the 

 species I have included under J belong more properly under F 

 and possibly even to the groups of birds with annual moult. 

 With much material for study, it has been impossible for me to 

 be positive about some species but their status will be discussed 

 later on under the species themselves. 



