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 aerial dance over, they alight in 

 separate couples on the tree tops, each couple 

 joining in a kind of duet of rapidly repeated, castanet- 

 like sounds. 



The displays of the wood-hewers, or Dendrocolap- 

 tidse, 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 liye 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 distance 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 like 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 

 P'Orbigney first remarked. Thus, in the red oven- 



