1896.] NATURAL SCIENCES OF PHILADELPHIA. 123 



individual bird passed through all those gradations ; or they have 

 taken a series of feathers from different individuals or different parts 

 of the same individual, which show regular gradations from one style 

 of coloration to another, as proof that each feather passes through 

 all those gradations. 



As a matter of fact, these mottled plumages are permanent for the 

 time being, and at each regular molt a greater proportion of the 

 adult plumage is assumed. Scarcely any two individuals, however, 

 correspond exactly in the amount of change that is effected at a given 

 molt ;'" hence a series of breeding birds taken during the late spring 

 or early summer, representing individuals of different age, will often 

 show a nearly complete series of intergrades between the two styles 

 of plumage, and there will, of course, be no signs of a molt. 



A study of several of the more recent examples that have been 

 brought forward to illustrate the actual change of color in feathers, 

 will be of interest in this connection. 



Dr. R. Bowdler Sharpe, in the Catalogue of Birds in the British 

 Museum, seems to regard this alleged phenomenon as of rather 

 common occurrence, and in some instances goes into much detail 

 with regard to the subject. This is especially the case in treat- 

 ing of Motacilla lugens,^^ in which he claims, not only a change 

 from gray to black in the plumage of the back, but also a remark- 

 able change in the color of the primaries and secondaries from 

 brownish to pure white, the adult plumage being assumed according 

 to Dr. Sharpe's theory, in the first spring. 



With the same material examined by Dr. Sharpe, and a little 

 more showing the molt in progress. Dr. Stejneger'^ shows conclusively 

 that this species requires several years to acquire the fully adult plum- 

 age, and that the changes in the color of the wing feathers is effected 

 by actual molt and not by a change in the color of each individual 

 feather. This shows conclusively the importance of having spec- 

 imens in the molt for examination and comparison, and what a 

 different aspect they may put upon the case. 



While combating the theory of direct color change in Motacilla 



^"It is not intended that only a part of the plumage is changed ; while this 

 may be true of the spring molt, the annual molt is always characterized by a 

 complete change, but, in the cases referred to, part of the new plumage comes 

 in exactly like the old, while in other parts the color of the new plumage is 

 ■diflerent. 



1^ Cat. Eds. Brit. Mus., X, 1885, p. 474. 

 12 Proc. U. S. Nat. Mus., 1892, p. 307. 



