6o BIRDS OF LA PLATA 



on the mound. When disturbed or persecuted by 

 other birds, they utter a peculiar cry, resembling 

 the shrill neighing of a horse. In disposition they 

 are most peaceable, and where they are abundant 

 all other birds soon discover that they are not as 

 other Hawks are and pay no attention to them. 

 When soaring, which is their favourite pastime, the 

 flight is singularly slow, the bird frequently remain- 

 ing motionless for long intervals in one place ; but 

 the expanded tail is all the time twisted about in the 

 most singular manner, moved from side to side, and 

 turned up until its edge is nearly at a right angle 

 with the plane of the body. These tail-movements 

 appear to enable it to remain stationary in the air 

 without the rapid vibratory wing-motions practised 

 by Elanus leacurus and other hovering birds; and 

 I should think that the vertebrae of the tail must 

 have been somewhat modified by such a habit. 



Concerning its breeding habits Mr« Gibson writes : 

 ** In the year 1873 I was so fortunate as to find a 

 breeding colony in one of our largest and deepest 

 swamps. There were probably twenty or thirty 

 nests, placed a few yards apart, in the deepest and 

 most lonely part of the whole * canadon.' They were 

 slightly built platforms, supported on the rushes and 

 two or three feet above the water, with the cup- 

 shaped hollow lined with pieces of grass and water- 

 rush. The eggs never exceeded three in a nest ; the 

 ground-colour generally bluish-white, blotched and 

 clouded very irregularly with dull red-brown, the 

 rufous tint sometimes being replaced with ash-grey." 



