50 BIRDS OF LA PLATA 
infrequently on a tree. Me Gibson describes one, 
which he found on the top of a thorn-tree, as a 
structure of large sticks, three feet in diameter, the 
hollow cushioned with dry grass. It contained two 
eggs, dull white, marked with pale reddish blotches. 
Mr. Gibson compared its cry to a “ wild human 
laugh,’’ and also writes: “* Its whereabouts may often 
be detected by an attendant flock of Caranchos 
(Polyborus tharus), particularly in the case of a young 
bird. As soon as it rises from the ground or from a 
tree, these begin to persecute it, ascending spirally 
also, and making dashes at it, while the Eagle only 
turns its head watchfully from side to side, the 
mere action being sufficient to avert the threatened 
collision.” 
Gay, in his Natural History of Chili, describes the 
affectionate and amusing habits of an Eagle of this 
species which he had tamed. It took great delight in 
playing with his hand, and would seize and pretend 
to bite one of his fingers, but really with as much 
tenderness as a playful dog displays when pretending 
to bite its master. It used also to amuse itself by 
picking up a pebble in its beak, and with a jerk of 
its head toss it up in the air, then seize it in its 
claws when it fell, after which it would repeat the 
performance. 
