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 exception is the handsome and loquacious whistling widgeon of La Plata, which has a pretty aerial performance. A dozen or twenty birds rise up until they appear like small specks in the sky, and sometimes 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. First, one bird among the rushes emits a powerful cry, thrice repeated; and this is a
and Dancing in Nature.
26?
note of invitation, quickly responded to by other birds from all sides as they hurriedly repair to the usual place. In a few moments they appear, to the number of a dozen or twenty, bursting from the rushes and running into the open space, and instantly beginning the performance. This is a tremendous screaming concert. The screams they utter have a certain resemblance to the human
