154 THE STRUCTURE AND LIFE OF BIRDS chap. 



the feathers. By far the most remarkable of such 

 movements are connected with flight. 



It is interesting to put side by side some of the most 

 wonderful forms of feathers, bearing in mind the like 

 origin of all : for instance, an Ostrich's plume, a 

 Penguin's tiny scale-like wing-feather, one of an 

 Albatross's mighty remiges, a Cassowary's plume with 

 its equal shafts, a hackle from the neck of a Barndoor 

 cock, a plume from a Bird of Paradise, a Lyre-bird's 

 tail feather, a spur from a Cassowary's wing (a great 

 wing feather that has lost its barbs so that the shaft 

 alone is left), one of the Motmot's two extraordinary 

 tail feathers, one of the grandest from a Peacock's 

 train, and, to complete the collection, one of the 

 stumpy business-like set with which a Woodpecker 

 props himself as he climbs. 



Feather Tracts. 



Except in the Penguin the feathers do not cover 

 the whole of the body, but only certain feather tracts. 

 The bare regions are called Apteria, and are some- 

 times devoid even of down — for instance, in the Wood- 

 pecker and the Sparrow-hawk. 



Our common birds have most of them a bare tract 

 down the breast, which is very convenient when you 

 wish to skin them. In most sea-birds you have to 

 work through a thick, almost impervious, mass of 

 feathers before you can begin operations. Feather 

 tracts, especially down the neck and back, have been 

 found very useful for purposes of classification. 



