201 



])iii^-nan t^Uo-vvinti- (1) section oi'barb.'s (rtniii) ,11. d (-, 3) interlocking 

 barbules (ndlii). 



tail, in birds wliicli possess full powers of fliglit, are always well- 

 doveloped and conspicuouslj' large (p. 203) . 



Seniipluinen are degenerate contour-feathers and have discontinuous 

 vanes. Sometimes they are of great size and beauty and are accordingly 

 nuicli prized for decorative purposes. For instance "Marabou" feathers 

 arc the sciuiplumcs of the Marabou and Adjutant-Storks. 



Dovjn-J'eatlicrfi arc very delicate in structure, the shaft, when present, 

 being very short and weak, whilst the barbs are long and fragile. 

 They are almost always hidden below the contour-feathers, but arc 

 occasionally exposed and form the ruff' round the neck of the Condor 

 and certain N'ultures. In water-birds these feathers form a thick under- 

 clothing recalling the under-fur of Mammals, and often, as in the 

 Swans and Eidcr-Ducks, have a considerable commercial value. Some 

 birds, such as the Game-birds, Pigeons, and Hornbills, have no 

 down-feathers. 



Filo-plunies are long hair-like feathers bearing a minute vane at the 

 ti(), and occur in clusters round the bases of the contour-feathers. In 

 some birds, for instance in the Cormoi'ants, they appear on the surface 

 of certain parts of the body, notably on the head and neck. 



Powder-dovm feat/iers- occur only in a few groups of birds, either 

 sj>arsely scattered over the body, as in Parrots and certain Hawks, or in 

 patches on tlie breast and thighs, as in the Herons. They are remark- 

 able for their extreme friability, constantly breaking up at their tips 

 into a fine powder, which feels smooth and almost greasy to the touch. 

 Nothing is known concerning the develoinncnt or use of these extra- 

 ordinary feathers. 



The long stiff bristles, which occur round the mouth of certain birds, 

 such as the Nightjars, or form eyelashes in others, for instance in the 

 Ostrich and Grouud-Hornbill, and the peculiar tuft which hangs from 

 tlie breast of the Turkey, are degenerate contour-feathci's, which have 

 lost their vanes. 



