214 BIRDS OF LA PLATA 



place is forsaken, the whole concourse leaving in a 

 body, or scattering in all directions over the sur- 

 rounding country ; and until the following summer 

 their movements depend entirely on food and water. 

 If the weather is dry the Gulls disappear altogether ; 

 and if grasshoppers become abundant the country 

 people wish for rain to bring the Gulls, When it 

 rains then the birds quickly appear, literally from the 

 clouds, and often in such numbers as to free the 

 earth from the plague of devastating insects. It is a 

 fine and welcome sight to see a white cloud of birds 

 settle on the afflicted district ; and at such times their 

 mode of proceeding is so regular that the flock well 

 deserves the appellation of an army. They sweep 

 down with a swift, graceful flight and settle on the 

 earth with loud, joyful cries, but do not abandon 

 the order of attack when the work of devouring has 

 begun. The flock often presents a front of over a 

 thousand feet, with a depth of sixty or seventy feet ; 

 all along this line of battle the excited cries of the 

 birds produce a loud, continuous noise ; all the birds 

 are incessantly on the move, some skimming along 

 the surface with expanded wings, others pursuing 

 the fugitives through the air, while all the time the 

 hindmost birds are flying over the flock to alight in 

 the front ranks, so that the whole body is steadily 

 advancing, devouring the grasshoppers as it pro- 

 ceeds. When they first arrive they seem ravenously 

 hungry, and after gorging themselves they fly to 

 the water, where after drinking they cast up their 

 food and then go back to renew the battle. 



