512 J. A. ALLEN ON BIRDS 



second, or the fifth, soon outstrip the others in growth, the wing in its increase approach- 

 ing more and more, through the different degrees of rapidity of growth of the different 

 quills, to its final form, — normally the quills all ending their growth, as they commenced 

 it. simultaneously. But with the first set the mature form for the species is not always 

 reached, nor, in some groups, with the second ; young birds, in genera with the middle 

 primaries longest in the mature wing, having the wing more rounded than the fully adult. 

 This I have seen exemplified in different species, but it is a fact especially marked in 

 Chrysomitris tristis ; in which, besides the difference in this respect between young and fully 

 mature birds, there is a similar one sometimes exhibited in the different sexes, the female 

 often having a more rounded and hence less perfect wing than the male. This latter I 

 have noticed also in other species, it being apparently more common in those with marked 

 sexual differences in plumage. Yet how often do we find definite wing formulas given in 

 specific diagnoses as though they were characters of the utmost value, proportional differ- 

 ences in the primaries being cited as conclusive evidence in eking out other faint indications 

 of specific diversity! Whereas, the individual range of variation in this respect is often 

 sufficiently great in either of several closely allied species, to cover the general range of 

 all ; hence, as already observed, this character of the proportions of the primaries, or of the 

 form of the wing, seems to be a generic rather than a specific one. 



In the category of generally approved specific distinctions, that of absolute size, as prob- 

 ably many ornithologists are now aware, is too variable to be a really distinctive feature 

 in strictly congeneric species. Thus the range in variation in measurement afforded by 

 either T. Pallasi or T. Swainsord, or of T. fuscescens, will cover the common range of the 

 three, a case of by no means rare occurrence. But the relative size of different parts has 

 been looked upon almost universally, and most naturally, as among the ultimata in specific 

 distinctions. But here, in making a large series of detail measurements, amounting to twenty 

 or more for each bird, I have been astonished at most unlooked-for variations in individuals 

 of the same species and sex, from one and the same locality, the variations amounting in some 

 cases, as, for example, in Colymbus lorguatus, 1 to twenty-five per cent, of the general mean ; 

 while in many small birds, as in different species of Fringillida;, Sylvicolida>, and Turdidoe, it 

 is almost as much, though less marked to the casual observer, from the smaller size of the 

 birds. Through these variations we find in the same species both slender and stout-built 

 birds, in which the character of slenderness or stoutness extends to all the different parts ; 

 also long tarsi accompanying short toes, long wings a short tail, or a short tail a long neck, 

 and that bills vary greatly in the proportion of thickness to length, and hence in their 

 general form; 2 differences wholly similar to the variations in stature, build, and general 

 physiognomy observable in any given race or nationality of men. What is claimed from 

 this is. that the fact of a marked individual variation existing anions; birds has not been 

 hitherto sufficiently recognized, from the fact that a sufficient number of individuals of any 

 species, taken at the same season and at one locality, have not been critically studied. Hence 

 it is that such differences as some of the above having been for the first time detected in 



1 In a series of fifteen specimens of C. torqualus in the Mu- the outer toe, 30 percent.; of the head, "28 per cent.; of the 



seum of Comparative Zoology, all from New England and culmen, 23 per cent. 



nearly all from Massachusetts, the variation in the length of 2 As we purpose soon to make puhlie some of the measure- 



the wing in the two extreme specimens amounts to 20 per ments on which these statements are based, we omit further 



cent, of the mean of the series; of the tarsus, 29 percent.; of details here. 



