10 The Ruffed Grouse 



Ptilosis— Types of feathers and their characteristics/ Before dis- 

 cussing the feather tracts and spaces, let us consider the character 

 and texture of the feathers themselves. This is known as ptilosis, or 

 plumage: 



Neossoptiles make up the natal down, distinguishable from simi- 

 lar feathers in the adult by the presence of pigment. They are the 

 tips of the barbs of the succeeding juvenile feathers, sometimes 

 called mesoptiles. Their length varies from six millimeters in the 

 capital and dorsal cervical tracts to thirteen millimeters in the sternal 

 and femoral. 



Filoplumes are degenerate feathers, appearing almost like hairs. 

 They arise from the skin elevations from which come also the teleop- 

 tiles and semiplumes. From zero to four may arise from these skin 

 elevations. They range from half to three-quarters the length of the 

 larger feathers. 



Plumulae are adult down feathers, similar to neossoptiles but 

 without pigment. They differ from semiplumes in the absence of a 

 rachis. Strictly speaking there are no plumulae in the grouse, but 

 those feathers resembling plumulae but having slight pigmentation 

 have been called by this name. 



Semiplumes are between plumulae and teleoptiles in character. 

 They are always covered with other feathers, are downy, but possess 

 a rachis. Large semiplumes, for all purposes merely downy teleop- 

 tiles, are found on the sides of the abdomen. Smaller ones occur in 

 the posterior part of the spinal tract, in the cervical spaces, beside 

 the primaries and many of the secondaries, and just above and below 

 the bases of the inner rectrices. 



Teleoptiles are the typical feathers of the adult— rectrices, remiges, 

 coverts, contour feathers, and others. They vary widely according to 

 modifications for various functions from the highly developed, 

 almost completely pennaceous (i.e. not downy) rectrices and 

 remiges to others difficult to distinguish from semiplumes. Some ex- 

 tremely modified teleoptiles are those of the eyelid, the oil gland, 

 the ear, and the anus. Some, as those of the eyelid and oil gland, are 

 probably functional and are small and modified of necessity; the 

 others are likely only vestigial. In these modified feathers the barbi- 

 cels are usually absent, the rachis ( oil gland ) is sometimes missing; 



^ For good photographs of several types of bird feathers, see Life magazine for 

 July 17, 1944, pp. 8-11. 



