272 The Naturalist in La Plata. 
upwards, like rockets, to a great height in the air, 
and, after wheeling about for a few moments, pre- 
cipitate themselves downwards with amazing 
violence in a wild zigzag, opening and shutting the 
long tail-feathers like a pair of shears, and producing 
loud whirring sounds, as of clocks being wound 
rapidly up, with a slight pause after each turn of 
the key. This aérial dance over, they alight in 
separate couples on the tree tops, each couple 
joining ina kind of duet of rapidly repeated, castanet- 
hike sounds. 
The displays of the wood-hewers, or Dendrocolap- 
tide, another extensive family, resemble those of the 
tyrant-birds in being chiefly duets, male and female 
singing excitedly in piercing or resonant voices, and 
with much action. The habit varies somewhat in 
the cachalote, a Patagonian species of the genus 
Homorus, about the size of the missel-thrush. Old 
and young birds live in a family together, and at 
intervals, on any fine day, they engage in a grand 
screaming contest, which may be heard distinctly at 
a distanve of a mile and a half. One bird mounts 
on to a bush and calls, and instantly all the others 
hurry to the spot, and burst out into a chorus of 
piercing cries that sound lke peals and shrieks of 
insane laughter. After the chorus, they all pursue 
each other wildly about among the bushes for some 
minutes. 
In some groups the usual duet-like performances 
have developed into a kind of harmonious singing, 
which is very curious and pleasant to hear. This 
is pre-eminently the case with the oven-birds, as 
D’Orbigney first remarked. Thus, im the red oven- 
