The Crested Screamer. 227 



spontaneous outbursts of a melody so powerful from 

 one of these large flocks, and though accustomed 

 to hear these birds from childhood, I have often 

 been astonished at some new effect produced by a 

 large multitude singing under certain conditions. 

 Travelling alone one summer day, I came at noon 

 to a lake on the pampas called Kakel a sheet 

 of water narrow enough for one to see across. 

 Ohakars in countless numbers were gathered along 

 its shores, but they were all ranged in well-defined 

 flocks, averaging about five hundred birds in each 

 flock. These flocks seemed to extend all round 

 the lake, and had probably been driven by the 

 drought from all the plains around to this spot. 

 Presently one flock near me began singing, and 

 continued their powerful chant for three or four 

 minutes ; when they ceased the next flock took up 

 the strains, and after it the next, and so on until 

 the notes of the flocks on the opposite shore came 

 floating strong and clear across the water then 

 passed away, growing fainter and fainter, until 

 once more the sound approached me travelling 

 round to my side again. The effect was very 

 curious, and I was astonished at the orderly way 

 with which each flock waited its turn to sing, 

 instead of a general outburst taking place after the 

 first flock had given the signal. On another occa- 

 sion I was still more impressed, for here the largest 

 number of birds I have ever found congregated at 

 one place all sung together. This was on the 

 southern pampas, at a place called Gualicho, where 

 I had ridden for an hour before sunset over a 

 marshy plain where there was still much standing 

 Q 2 



