BIRDS OF ARGENTINA, PARAGUAY, URUGUAY, AND CHILE 19 

 NOTES ON MIGRATION 



Though ordinarily we may think of extensive and widespread 

 migratory movements among birds as something more or less pe- 

 culiar to the Northern Hemisphere, yet on investigation we find 

 pronounced migrations among the birds of South America, espe- 

 cially in the southern part of the continent. The migratory flight 

 in the latter region may be considered as of two kinds, first, that 

 of birds come from North America for the period of the northern 

 winter, and, second, that of species that pass south to breed, and 

 with the close of the period of reproduction withdraw again toward 

 the Tropics. 



Though a number of passerine and other birds from North 

 America come conmionly to the northern part of South America, 

 comparatively few of these species pass as far south as the section 

 covered by Paraguay, Uruguay, Argentina, and Chile. Among 

 the few of the smaller land species that perform this extended 

 flight, the barn swallow and the bobolink are worthy of mention, 

 especially the latter, as though the barn swallow occurs during the 

 northern winter months from the West Indies southward, the bobo- 

 link withdraws wholly into the Chaco. The yellow-billed cuckoo, 

 cliff swallow, olive-backed thrush, nighthawk, and Swainson's hawk 

 are of more or less common occurrence in the northern half of the 

 region in question, but are not found in abundance. In addition 

 to these may be mentioned the parasitic and long-tailed jaegers 

 (that have been recorded casually, but that occasionally at least, 

 occur in great abundance along the coast of Buenos Aires), Cabot's, 

 royal, and arctic terns, and the red and northern phalaropes. Tl>e 

 great body of North American migrants, how^ever, are shore birds, 

 some of which as the two yellowlegs, the sanderling, and the spotted 

 sandpiper have extended winter ranges, while others as the Hud- 

 sonian godwit, the upland plover, the buff -breasted, pectoral, 

 Baird's, and white-rumped sandpipers find in the pampas and in 

 Patagonia their winter metropolis. With these last may be men- 

 tioned the Eskimo curlew now nearly, if not actually, extinct. 



A few individuals of these northern species arrive in the south in 

 July and August, but their main southward flight occurs from Sep- 

 tember to November. In other words, they pass south with the 

 coming of fall in the Northern Hemisphere, and below the Equator 

 follow the advance of southern spring to their winter home, remain 

 during the southern summer, and with the coming of colder weather 

 in February and March withdraw northward until they cross the 

 Equator and follow the northern spring in its advance to their 

 breeding grounds in the northern United States, Canada, and Arctic 



