160 BIRDS OF LA PLATA 
The male is a solitary Sird, 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. 
