20 BULLETIN 133^ UNITED STATES NATIONAL MUSEUM 



America. Their itinerary thus takes advantage of the shifting sea- 

 sons in both continents. 



Because some of these species now or formerly occurred in the 

 Argentine in great abundance, it has been held by some that there 

 are in these species two groups of individuals, a northern body that 

 breeds in North America and migrates south to clement regions in 

 Mexico or Central America, and a southern group, that occupies a 

 breeding ground in Patagonia, the islands of Antarctic seas, or even 

 the great Antarctic Continent, that comes north to winter in the 

 Argentine. This belief was based in part upon the seemingly irreg- 

 ular occurrence of some of these migratory birds, with records 

 (scattered and few) of certain species that were found on the pampas 

 during the northern breeding season, and in part upon disbelief in 

 the powers of flight in creatures apparently small and weak. There 

 are certain species, such as the pied-billed grebe, cinnamon teal, ful- 

 vous tree duck, and others that have a breeding range in both North 

 and South America. In some of these individuals from the two 

 colonies appear indistinguishable; in others the two groups may 

 differ slightly in minor characters. There has never been any cer- 

 tain indication, however, of the breeding south of the Equator of 

 such species as the golden plover, Hudsonian godwit, the yellow- 

 legs, and other species considered as migrants from the north. 

 The scattered individuals that remain in Argentina during the 

 northern summer are wounded, sterile, or otherwise diseased indi- 

 viduals that have been unable to perform the long flight northward, 

 or that have lacked the physiological incentive to do so. The few 

 supposed occurrences of their nesting have, on investigation, proven 

 erroneous, and the migration and seasonal movements of these spe- 

 cies is so well understood that there is no question that they nest 

 in the north and pass south of the Equator only in migration. Data 

 from birds banded in the north eventually will authenticate these 

 facts. 



In their movements after reaching the northern coast of South 

 America these northern species have three main routes, one north 

 and south along the Atlantic coast, one that passes along the Pacific 

 coast line, and a third that follows the great interior north and 

 south river system of the Paraguay and Parana. Some of the birds 

 that follow this last route on their southern journey apparently drive 

 straight south across the pampas until they strike the southern coast 

 of Buenos Aires, and then swing around to follow up to some win- 

 tering ground in the eastern pampas, or near the mouth of the Rio 

 de la Plata. In November, on the eastern coast of Buenos Aires, I 

 witnessed a curious phenomenon where one line of northern migrants 

 came driving south down the coast, and a second, traveling in the 

 opposite direction, came sweeping up from the south. My only sup- 



