BIRD MIGRATION 9 



are separated by very variable distances. Many species from Canada 

 winter in the United States, as the tree sparrow, jimco, and snowflake ; 

 others nesting in northern United States winter in the Gulf States, 

 as the chipping, field. Savannah, and vesper sparrows, while more 

 than a hundred species leave the United States for the winter and 

 spend that season in Central or even in South America. Nor are they 

 content with journeying to northern South America, but many cross 

 the Equator and pass on to the pampas of Argentina and a few even 

 to Patagonia. Among these long-distance migrants are some of our 

 commonest birds ; the scarlet tanager (PL IV) migrates from Canada 

 to Peru; the boboUnks (fig. 1 and PL I) that nest in New England 

 probably ^vinter in Brazil, as do purple martms, cliff swallows, barn 

 swallows, nighthawks, and some thrushes, which are their companions 

 both summer and winter. The black-poU warblers that nest in Alaska 

 winter in northern South America, at least 5,000 miles from the 

 summer home. The land bird with the longest migration route is 

 probably the nighthawk, which occurs north to Yukon and south, 

 7,000 miles away, to Argentina. 



But even these distances are surpassed by some of the water birds, 

 and notably by some of the shorebirds, which as a group have the 

 longest migration routes of any birds. Nineteen species of shore- 

 birds breed north of the Arctic Circle, every one of which visits South 

 America in winter, six of them penetrating to Patagonia, a migration 

 route more than 8,000 miles in length. 



The world's migration champion, however, is the arctic tern (fig. 3 

 and PL II). It deserves its title of "arctic," for it nests as far north 

 as land has been discovered; that is, as far north as the bird can find 

 anything stable on which to construct its nest. Indeed, so arctic 

 are the conditions under which it breeds that the first nest found by 

 man in this region, oidy 7^-° from the pole, contained a downy chick 

 surrounded by a waU of newly fallen snow that had been scooped out 

 of the nest by the parent. When the young are full grown the entire 

 family leaves the Arctic and several months later they are found 

 skirting the edge of the Antarctic continent. 



What their track is over that 11,000 miles of iutervenmg space 

 no one knows. A few scattered individuals have been noted along 

 the United States coast south to Long Island, but the great flocks 

 of thousands and thousands of these terns which range from polo to 

 polo have never been noted by an ornithologist competent to indi- 

 cate their j)ref erred route and their time schedule. The arctic terns 

 arrive in the far north about Juno L5 and leave al)out August 25, 

 thus staying 14 weeks at the nesting site. They prol)a})ly spend a 

 few weeks longer in the winter than in the summer homo, and tliis 

 would leave thorn scarcely 20 weeks for tlio round trip of 22,000 

 miles. Not less than 150 miles in a straiglit lino must bo theii' daily 



70048°— Bull. 185— l.'i 2 



