160 BIRDS OF LA PLATA 



The male is a solitary bird, and feeds chiefly on 

 the ground, running rapidly about in open places 

 like a Muscisaxicola. It is also frequently seen 

 perched conspicuously on the summit of a tall stalk 

 or bush, and occasionally making a dart into the air 

 after passing insects, showing in this habit his rela- 

 tionship with the Tyrant-birds* But he perches on 

 an elevation less to watch for insects than for the 

 purpose of his curious spectacular performance. This 

 highly eccentric habit is strikingly like that of Cnipo- 

 legus hudsoni; and I have no doubt that all the 

 Cnipolegi possess similar habits. Both birds perch 

 on a conspicuous place, upright, motionless, and 

 looking more like grotesque little automata than 

 living things ; they both also leave the perch sud- 

 denly, as if shot from it by means of a steel spring. 

 This singularly sudden movement, and the motion 

 of the wings, rapid as in the Humming-bird, or 

 shut and opened alternately and exhibiting the white 

 wing-colour in a series of flashes, seems related to 

 the conspicuous white mark. In both species also, 

 the wings make a humming sound during flight. 

 The motions of the Silverbill are, however, in some 

 respects different from those of the Cnipolegus. 

 Springing from its perch at intervals, it darts verti- 

 cally to a height of about fifteen yards, then turns a 

 somersault, uttering at the same moment a shrill- 

 sounding little cry, after which it drops down again 

 and alights on its perch suddenly, as if jerked back 

 to it, and there remains stiff, erect, and motionless 

 as before. 



