Fear in Birds. 95 



hawk (Rostrhamus 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 



