200 BULLETIN Of iHE 



Variation in the Length of the Folded Wing and the Tail. — The 

 measurements given in the following table (Table B) sufficiently illus- 

 trate the variation in the length of the folded wing in fully mature speci- 

 mens of the same sex and species, while Table C indicates the 

 variation in the length of the tail, in specimens of a similar char- 

 acter. All the specimens, with a few exceptions, were taken within 

 a few miles of Cambridge ; the others are mainly also from Eastern 

 Massachusetts, a few * being from a single locality in Florida. The 

 series from which these extremes are taken embrace ordinarily not 

 more than twenty-five or thirty specimens ; with larger suites the 

 differences would in many cases doubtless be much increased. The 

 largest and smallest only are taken, between which, however, there 

 is every gradation. The difference between these extremes is indicated, 

 and also the percentage of the variation, based on the average of the 

 two extremes. The amount of the variation in the length of the folded 

 wing ranges, as will be seen from the table, from twelve to twenty-one 

 per cent of the average length. In the tail the amount of variation in 

 respect to length ranges from fourteen to twenty-three per cent. The 

 different species vary considerably in respect to the amount of variation 

 each presents, some being much more variable than others. It should 

 be stated, however, that as a general rule the widest extremes, or the 

 highest percentages of variation, occur in those species of which the 

 greatest number of specimens has been examined. It will also be noticed 

 that the tail usually varies more than the wings. In species with a 

 relatively long tail the percentage of variation in the length of this 

 member is found to be greater than in those species in which it is of 

 medium length or short, as would have been naturally expected. In 

 several cases the greater differences occur between females, but this 

 may be a mere coincidence. 



In this connection it may be added that the variation proves to be 

 much less between specimens of the same species and sex when taken 

 at a single locality in the breeding season than when taken during the 

 period of migration. In many instances specimens of the same species 

 may be obtained at one locality which shall represent the whole range 

 of its geographical variation, as well as- its individual variation, as in 

 the case of those species which breed far to the North, but migrate in 

 winter to the tropics, being thus but transient visitors to the temperate 

 portions of the United States. 



* Those of Mimus pc'iyglottus, Cardinalis virdnianus, Picus borealis. 



