BIRDS. 323 



in Fig. 242.) At the upper part of the windpipe is an organ 

 (the glottis, or superior larynx) hy which the size of the 

 aperture seems to he regulated. At the lower part is placed 

 the true organ of voice in hirds (the inferior larynx) ; and, in 

 all those which possess the vocal powers in the highest per- 

 fection, this part is furnished with five pair of nerves. "The 

 tube of the windpipe," says Mr. Yarrell, " is composed of 

 two membranes, enclosing hetween them numerous cartilagi- 

 nous or hony rings, forming a cylinder more or less perfect 

 from end to end. "* The tube differs in its length, its diameter, 

 and its substance, in different species; and in some it exhihits 

 convolutions which modify its powers. " The principle upon 

 which the organs of voice in hirds is founded, is that which 

 prevails in wind instruments generally; the notes in the 

 ascending scale being produced hy a corresponding contraction 

 of the diameter or the length of the tube, and vice versa." 



Such is the description given by physiologists of the 

 mechanism which produces the loud note of the Wild Swan, 

 the booming of the Bittern, the cawing of the Rook, the 

 hooting of the Owl, and the wild screams which, heard amid 

 the native haunts of the sea-fowl, harmonise with the surging 

 sea. Birds, as we all know, can be taught to imitate the 

 tones of the human voice; nor is this limited to the Parrot; 

 the power is enjoyed, among our native birds, by the Raven, 

 the Magpie, the Jay, and the Starling. So distinctly have 

 Ravens been taught to articulate short sentences, that one 

 living at Chatham, "in the vicinity of the guard-house, has 

 more than once turned out the guard, who thought they were 

 called by the sentinel on duty."f 



The power of imitation reaches, perhaps, its highest per- 

 fection in the Mocking-bird of America. So perfect is his 

 performance, that not only the experienced ear of the fowler 

 is deceived, but even birds themselves are imposed upon. In 

 a domesticated state he finds equal scope for the versatility 

 of his powers, and his doings have been most graphically 

 recorded by Wilson, in his American Ornithology: "He 

 whistles for the dog; Csesar starts up, wags his tail, and runs 

 to meet his master. He squeaks out like a hurt chicken, and 

 the hen hurries about, with hanging wings and bristled 

 feathers, clucking to protect its injured brood. The barking 



* British Birds, vol. ii. p. 71. 



f Quoted by Mr. Yarrell, from Swainson and Richardson. 



