PLUMAGE. 39 



these are a continuation of the covering of the back ; and the 

 second support the tail feathers on the upper side, and are strong 

 in proportion, as these are adapted for action in flying. In birds 

 which use the tail as the means of support in fixing themselves 

 upon upright surfaces, as is the case in the Woodpeckers, the 

 upper tail coverts are very strong and close, and so thick is their 

 array, as to give that organ the same stiffness as a powerful 

 wing. In those birds, also, which have to take wing from the 

 water, and yet have not the feet webbed and placed far back- 

 wards, so as to support them when rising, the tail-coverts are 

 peculiarly strong, in order to support the tail feathers, which 

 are the principal fulcra from which the bird gets into the air. 



10. The vent feathers and under tail-coverts, which cover the 

 hinder part of the bird ; and in those birds in which the tail 

 feathers are long and stiff, and much used in the act of flying, 

 support the under side of these feathers, in the same manner as 

 the under-coverts support the quills of the wings. In those birds 

 which have a habit of flirting up the tail, the under-coverts are 

 longer and stronger than in those which have no such habit. 



The tail feathers require no reference. They vary much in 

 their numbers and length, and also in the form of their termina- 

 tions, and the motions which the bird can communicate to them. 

 In some birds the whole, or, at least, great part, of these feathers 

 appear to be merely ornamental, which of course means nothing 

 more than that their uses have not been observed. In general, 

 however, they act both as a rudder in flying, and as a means of 

 directing the motion upwards or downwards. Analogy would 

 indeed lead us to suppose that their chief use is in the upward 

 and downward motion, because their greatest surface is generally 

 horizontal. The analogy is further confirmed by the fact, that 

 many of the low-flying birds have the breadth of the closed tail 

 in the vertical plane, though these also can, in general, spread it 

 out like a fan when they fly. 



The other feathers are to be considered rather as the clothing 

 of the bird than as active instruments in its flight, or as auxiliaries 

 in its motions upon the land or the water. But still they are 

 not less worthy of notice, both in the distinguishing of one bird 

 from another, and in tracing how well all the parts of birds are 

 adapted to their general habits and their haunts. These ordinary 

 feathers are imbricated that is, they are placed one over the 

 edges of two as slates or tiles are in a covering of a roof. By 

 means of this arrangement, all the parts of the bird are equally 

 feathered, and so they are equally proof to the action of the at- 

 mosphere. The lines in which the several rows of feathers are 

 placed, form very curious curves, and their shafts diverge or 



