94 The Naturalist in La Plata. 
such an instinct as that ; and in regions where hawks 
are extremely abundant most of the birds would be 
in a constant state of trepidation. On the pampas 
the appearance of the comparatively harmless 
chimango excites not the least alarm among small 
birds, yet at a distance it closely resembles a hen- 
harrier, and it also readily attacks young, sick, and 
wounded birds; all others know how little they 
have to fear fromit. When it appears unexpectedly, 
sweeping over a hedge or grove with a rapid flight, 
it is sometimes mistaken for a more dangerous 
species; there is then a little flutter of alarm, some 
birds springing into the air, but in two or three 
seconds of time they discover their mistake, and 
settle down quietly again, taking no further notice 
of the despised carrion-eater. On the other hand, 
T have frequently mistaken a harrier (Circus cinereus, 
in the brown state of plumage) for a chimango, and 
have only discovered my mistake by seeing the com- 
motion among the small birds. The harrier I have 
mentioned, also the C. macropterus, feed partly on 
small birds, which they flush from the ground and 
strike down with their claws. When the harrier 
appears moving along with a loitering flight near 
the surface, it is everywhere attended by a little 
whirlwind of alarm, small birds screaming or chirp- 
ing excitedly and diving into the grass or bushes ; 
but the alarm does not spread far, and subsides as 
soon as the hawk has passed on its way. Buzzards 
(Buteo and Urubitinga) are much more feared, and 
create a more widespread alarm, and they are 
certainly more destructive to birds than harriers, 
Another curious instance is that of the sociable 
