562 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1910. 



THE NATAL OR BIRTH PLUMAGE. 



Like the young of many other birds, the ostrich chick at hatching 

 is already provided with feathers in the form of down. This is the 

 natal or birth j)lumage, and consists of onty down feathers, 1 which 

 are very different from the feathers which will clothe the bird later. 

 Some of these down feathers, taken from the back, sides, and under 

 surface, are shown in the illustration. (PI. 1, fig. 1.) 



Though differing somewhat in size, the down feathers are of the 

 same character all over the body and wings, a contrast to the various 

 kinds of feathers which the bird produces later. They consist of 

 small tufts of plumules, differing in length, and all starting from 

 about the same level, there being no shaft or stem, as in the later 

 feathers. 2 ach tuft consists of from 10 to 20 or more plumules, of 

 which at least 4 are much longer than the others, being about 2£ 

 inches in length in the side feathers but only about half as long on 

 the back. A plumule is made up of a central axis or barb with 

 small delicate barbules on each side. Toward their free end the 

 larger plumules are without barbules, and on the down feathers of 

 the back are prolonged into a rather coarse, flat, curled, strap-like 

 portion, but on the feathers of the side and below they are narrower 

 and more hair like. The flat naked parts of the barbs give a bristly 

 hedgehog-like appearance to the young chick, and stand out con- 

 spicuous^ against the rest of the plumage. (PI. 1, fig. 2.) Most of 

 the remaining plumules have barbules all along their length and vary 

 in size from an inch and a half to half an inch, while two or three 

 are shorter. These soft delicate plumules give the downy character 

 to the under part of the plumage of the young chick, though this is 

 somewhat obscured toward the surface by the bristle-like character 

 of the barbs of the long plumules. (PI. 1, fig. 2.) 



Even at the time of hatching it is possible to distinguish in the 

 natal down great differences in the feather-producing capacity of 

 various strains of birds. The down feathers in some strains are almost 

 double the size of the feathers in other strains, while others again 

 are denser and more glossy. 



At all ages the neck and head of the ostrich are, as regards their 

 plumage, sharply distinguished from the rest of the body. These 

 parts are sometimes described as naked, but as a matter of fact they 

 are thickly covered by feathers which are much smaller than those 



1 Down feathers are sometimes termed " plumules," but in ostrich feather terminology it 

 is best to use plumule for each barb and the barbules attached to its sides. Thus each 

 constituent of a down feather will be a plumule, as well as each separate part of the 

 flue arising from the shaft in the adult plume. 



- It has lately been shown that both the shaft and quill are absent from the first 

 down feathers of birds, the barbs of the down feather passing without interruption 

 into the new feather below. In the large down feathers of the ostrich, however, there 

 is fully half an inch of quill. 



