230 The Naturalist in La Plata. 



exercises that in bright warm weather, in winter 

 and spring, it spends a great part of the day in the 

 upper regions of the air. On the earth its air is 

 grave and its motions measured and majestic, and 

 it rises with immense labour, the wings producing 

 a sound like a high wind. But as the bird mounts 

 higher, sweeping round as it ascends, just as 

 vultures and eagles do, it gradually appears to 

 become more buoyant, describing each succeeding 

 circle with increasing grace. I can only account 

 for this magnificent flight, beginning so laboriously, 

 by supposing that the bubble space under the skin 

 becomes inflated with an air lighter than atmo- 

 spheric air, enabling a body so heavy with wings 

 disproportionately short to float with such ease and 

 evident enjoyment at the vast heights to which the 

 bird ascends. The heavenward flight of a large 

 bird is always a magnificent spectacle ; that of the 

 chakar is peculiarly fascinating on account of the 

 resounding notes it sings while soaring, and in 

 which the bird seems to exult in its sublime power 

 and freedom. 



I was once very much surprised at the behaviour 

 of a couple of chakars during a thunderstorm. On 

 a still sultry day in summer I was standing watch- 

 ing masses of black cloud coming rapidly over the 

 sky, while a hundred yards from me stood the two 

 birds also apparently watching the approaching 

 storm with interest. Presently the edge of the 

 cloud touched the sun, and a twilight gloom fell on 

 the earth. The very moment the sun disappeared 

 the birds rose up and soon began singing their long- 

 resounding notes, though it was loudly thundering 



