266 The Naturalist in La Plata. 



downwards with amazing violence, doubling about 

 in the most eccentric manner ; and when close to 

 the surface rising again to repeat the action, all the 

 while making the air palpitate for miles around with 

 their hard, metallic cries. Other ibises, also birds 

 of other genera, have similar aerial performances. 



The displays of most ducks known to me take 

 the form of mock fights on the water ; one excep- 

 tion is the handsome and loquacious whistling 

 widgeon of La Plata, which has a pretty aerial per- 

 formance. A dozen or twenty birds rise up until 

 they appear like small specks in the sky, and some- 

 times disappear from sight altogether ; and at that 

 great altitude they continue hovering in one spot, 

 often for an hour or longer, alternately closing and 

 separating ; the fine, bright, whistling notes and 

 flourishes of the male curiously harmonizing with 

 the grave, measured notes of the female ; and every 

 time they close they slap each other on the wings 

 so smartly that the sound can be distinctly heard, 

 like applauding hand-claps, even after the birds have 

 ceased to be visible. 



The rails, active, sprightly birds with powerful 

 and varied voices, are great performers ; but owing 

 to the nature of the ground they inhabit and to 

 their shy, suspicious character, it is not easy to 

 observe their antics. The finest of the Platan rails 

 is the ypecaha, a beautiful, active bird about the size 

 of the fowl. A number of ypecahas have their 

 assembling place on a small area of smooth, level 

 ground, just above the water, and hemmed in by 

 dense rush beds. Pirst, one bird among the rushes 

 emits a powerful cry, thrice repeated ; and this is a 



