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 aérial 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 aérial 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, whistlmg 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 
