Fear in Birds, 
95 
bcwk (Rostrliamns sociabilis). This bird spends the 
summer and breeds in marshes in La Plata, and 
birds pay no attention to it, for it feeds exclusively 
on water-snails (Ampullaria). But when it visits 
woods and plantations to roost, during migration, 
its appearance creates as much alarm as that of a 
true buzzard, which it closely resembles. Wood- 
birds, unaccustomed to see it, do not know its 
peculiar preying habits, and how little they need 
fear its presence. I may also mention that the birds 
of La Plata seem to fear the kite-like Elanus less 
than other hawks, and I believe that its singular 
resemblance to the common gull of the district in 
its size, snowy-white plumage and manner of 
flight, has a deceptive effect on most species, and 
makes them so little suspicious of it. 
The wide-ranging peregrine falcon is a common 
species in La Plata, although, oddly enough, not 
included in any notice of the avifauna of that re- 
gion before 1888. The consternation caused among 
birds by its appearance is vastly greater than that 
produced by any of the raptors I have mentioned ; 
and it is unquestionably very much more destruc- 
tive to birds, since it preys exclusively on them, 
and, as a rule, merely picks the flesh from the head 
and neck, and leaves the untouched body to its 
jackal, the carrion-hawk. When the peregrine 
appears speeding through the air in a straight line 
at a great height, the feathered world, as far as one 
is able to see, is thrown into the greatest commo- 
tion, all birds, from the smallest up to species large 
as duck, ibis, and curlew, rushing about in the air 
as if distracted. When the falcon has disappeared 
