1909] Beebe: Tail Feathers of the Motmot. 147 



1st. They were slow in starting, but became visible beyond the 

 upper tail-coverts in three weeks and on November 8th had 

 reached a total length of four and one half inches. A compact, 

 unbroken blood sheath surrounded the shaft to within three 

 inches of the tip. Several days previous to this the barbs had 

 been observed to be in disorder as they emerged from the sheath 

 and on one occasion the bird was seen to preen the right feather, 

 pick off a bit of broken sheath and with it several barbs ! 



On November 8th the denudation had proceeded to a con- 

 siderable extent and the left feather presented the appearance 

 seen in Fig. 45. The right side of the shaft is comparatively 

 clean while the left side is as yet only partially denuded. 



The blood sheath on the right feather was one and three- 

 quarter inches in length and encroached on the area of normal 

 denudation for the last quarter inch. With a pair of pliers I 

 gently pried up the dry end of the sheath and with it came four 

 barbs, leaving two, still affixed to the shaft, so firmly attached 

 that a gentle rubbing did not detach them. 



There is not the slightest chance that the bird could have 

 removed this bit of sheath with greater care than did I, so we 

 must conclude that the unusual physiological weakness of the 

 barbs which was so pronounced in the previous pair of feathers 

 that they were perfectly denuded on being freed of fhe/sheath, 

 was continued, but in a less degree in the present set of rectrices. 

 In the succeeding set, perhaps a normal balance will be attained.* 



The objection may be raised that this is all a result of ab- 

 normal ecological conditions surrounding a captive bird, but it 

 must be remembered that in the several sets of feathers grown 

 before I began my experiments, the feathers attained their full 

 length before being denuded. 



Mr. F. M. Chapman has called my attention to two interest- 

 ing specimens of Eumomota superciliaris recently received by 

 the American Museum from Nicaragua. In this species the 

 denudation of the tail-feathers reaches an extreme, the central 

 pair of rectrices extending four and a quarter inches beyond the 

 others, with almost three inches of bare shaft. 



In the two specimens mentioned, the central tail-feathers 

 are only partly grown, with only a portion of the denuded area 

 out of the sheath. The web on this portion shows an extreme 

 degeneration, comparable to the normal condition in the tail of 



*December 4, 1909. This is confirmed at the present date, when the tail 

 feathers have emerged with unbroken vanes from their sheaths, and the bird thus 

 proved to be in normal condition again. 



