i68 THE MIGRATIONS OF BIRDS 



those whose eggs have been destroyed and their 

 attempts at rearing a family thus frustrated. With 

 no further cause to remain in the north, these may 

 push rapidly southward and form our early mi- 

 grants. However we may attempt to explain the 

 phenomenon, the facts remain that many birds of 

 this group start south very early, so that by the 

 middle of July in the northern United States mi- 

 gration is well under way in a number of species. 

 It is of interest to note that passage southward in 

 m^any individuals is rapid. In 191 2, in Porto Rico, 

 the spotted sandpiper arrived from the north on 

 July 9, and the solitary sandpiper on July 29. In 

 1920, in southern South America, I noted the be- 

 ginning of migratory movement from the north 

 among these birds on July 31, with the arrival of 

 the lesser yellow-legs on lagoons near Las Palmas, 

 Chaco. The solitary sandpiper reached the town 

 of Formosa on the Rio Paraguay on August 23; 

 while during the first week of September, when I 

 had penetrated north to Puerto Pinasco in northern 

 Paraguay, migration began in earnest, and a steady 

 stream of sandpipers and plover passed southward 

 through the Chaco throughout the month. This 

 southward movement was still in force during Octo- 

 ber when I was in the open pampas of eastern 

 Buenos Aires, and continued without appreciable 

 abatement until the close of the first week in No- 



