MIGRATION AMONG SHORE-BIRDS 171 



Heavy rains that flood new areas in the pampas may 

 frequently bring small flocks of shore-birds in search 

 of new feeding grounds, but such movements are 

 of slight extent and affect comparatively few indi- 

 viduals. A period of moult is at hand and the birds 

 are inactive. Change in behavior is especially 

 marked in the two species of yellow-legs, which be- 

 come as quiet in notes and demeanor as small sand- 

 pipers or plover, quite in contrast to their noisy 

 greeting of intruders in their flights north of the 

 Equator. They remain thus during the months 

 that mark the northern winter. 



The impulse toward the return flight to the north 

 comes early; for at the close of January in 1921 I 

 noted a slight movement among golden plover on 

 the eastern coast of Uruguay. On February 7 up- 

 land plover began passing northward in small 

 numbers through eastern Uruguay, and on the fol- 

 lowing day pectoral sandpipers began their flight. 

 These early individuals must make frequent long 

 stops, so that their northward flights extend over 

 a considerable period of time, since their breeding 

 grounds are not open to them until a much later 

 date. Slow increase in northward migration was 

 observed during February, and by the close of the 

 first week in March the movement was in full swing. 

 The first week in April marked its culmination, and 

 by the end of that month decrease in shore-birds 



