﻿EXTERNAL ANATOMY. WING FEATHERS. 91 



but by their peculiar shape, and by the great develop- 

 ment of the secondaries ; these latter being often so long, 

 as nearly to equal the primary quills. This structure, in 

 fact, is the very opposite to that which we see in the 

 wings of the humming-birds, where the secondary 

 quills are so small that they become almost obsolete. 

 Indications, showing a tendency to this structure, may 

 be traced in many perching birds possessed of rounded 

 wings ; but those which we term rasorial differ 

 from these last sufficiently to authorise a distinct name 

 being applied to them. This will be evident on ex- 

 amining the wing of a partridge (Tetrao Perdioo L.), 

 and comparing it with any of the common birds we 

 have already named. The primary quills, in their 

 substance, have an unusual strength and rigidity : 

 their shape is almost falcate, and their form very nar- 

 row ; their curved shape gives to the wing a great 

 degree of convexity, and also indicates much strength ; 

 although, when the wing is closed, the primary quills 

 are hardly half an inch longer than the tertials, while 

 the secondaries are near three-fourths as long as the 

 primaries. It is well known that the noiseless flight of 

 the owl originates in the looseness, or rather the discon- 

 nection of the points, of the laminae of the quills, which 

 breaks the sudden resistance which the act of flight 

 makes to the air : it may therefore be supposed that a 

 wing, constructed on an entirely opposite principle, 

 would have as opposite an effect ; and this we accord- 

 ingly find. The wing of the partridge, from the pecu- 

 liar rigidity and compactness of its quill feathers, may 

 be said with truth to cut the air ; and as the owls are 

 the most silent flyers of all birds, the partridges are the 

 most noisy : the sudden whirring produced by their 

 wings on first arising, is entirely caused by the sharp- 

 ness and equality with which the air is beat, and is 

 probably intended to startle the intruder from that 

 fixed attention he would otherwise pay to his game. 

 In the Brazilian Tinamou partridges (Crypturus), the 

 lesser quills and the tertials are more developed than in 



