GENESIS OF FAULT-BARS IN FEATHERS. 337 



defects seem to occur more frequently in the juvenal plumage 

 (of D wight) than in the others. 



Evident defects appear in all the feather-tracts or pterylae ; but 

 in a particular bird, and usually in a particular species, certain 

 tracts show them in greater numbers than do others. In the 

 ring dove, Turinr risorius, the order of frequency of occurrence 

 is : rectrices, remiges, wing coverts, etc. In Galliis the order is : 

 remiges, rectrices, wing or body coverts, etc. 



In an Individual Feather. — In the feather there may be pro- 

 duced at any point in its length, either of the five types of 

 abnormality. In some birds {G alius) the distal part of the 

 feather oftener shows the defective areas ; the proximal end, the 

 deep constrictions (type 4), while we get defective lines (type 3) 

 in one form or another at all points in the feather's length. 



The recognition of weakened areas as universal in feathers 

 throws a new light on the rather over-discussed subject of feather 

 abrasion. That there are birds whose feathers " normally " have 

 the barbules broken off at certain fairly definite points in the more 

 distal barbs has been observed by Meves, 1 Chapman, 2 Dwight 3 

 and others. Meves and Chapman have noted, too, that the barb 

 itself may be broken near the distal end. I have seen several 

 cases among wild birds of the breaking of a series of barbs at 

 the point where they were crossed by the same defective line, 

 and am convinced that further study will prove that most feather 

 abrasions occur by the breaking away, as a single piece, of that 

 portion of a barb which occupies the space between two fault-bars. 

 That such breaks do occur at the fault-bars I have often proved 

 by pulling the distal end of a series of barbs and noting the point 

 at which they break. A feather treated in this way is shown in 

 PI. XIII., Fig. 7. 



1 Meves, W., " Uber die Farbenveranderung der Yogel," Jour, fur Ornith., Bd. 



3, i855- 



2 Chapman, F. M., "On the Changes of Plumage in the Snowflake,' ' Amer. Mus- 

 Nat. Hist., Vol. 8. 



3 Dwight, J., Jr., "The Sequence of Plumages and Moults in the Passerine Birds 

 •of New York," Ann. N. Y. Acad. Set., Vol. 13, No. I. 



