The palm warbler {Dendroica palmar urn) which breeds from Nova 

 Scotia and Maine west and northwest to southern Mackenzie, has been 

 separated into two subspecies. Those breeding in the interior of 

 Canada {D. p. palmar um) make a 3,000-mile journey from Great 

 Slave Lake to Cuba, passing through the Gulf States early in October. 

 After the bulk have passed, the palm warblers from the Northeastern 

 States and Provinces (D. p. hypochrysea) drift slowly into the Gulf 

 Coast region, where they remain for the winter. Their migratory 

 journey is about half as long as that of the northwestern subspecies. 



There is no invariable law governing the distance of migration, al- 

 though in general it is found that where a species has an extensive 

 range, the subspecies that breed farthest north go farthest south to 

 spend the winter. 



Fall flights not far south of breeding ranges 



Some other species that have extensive summer ranges, for instance 

 the pine warbler, rock wren, field sparrow, loggerhead shrike, and 

 black-headed grosbeak, are found to concentrate during the winter 

 season in the southern part of the breeding range, or to occupy addi- 

 tional territory that is only a short distance farther south. The entire 

 species may thus be confined within a restricted area for the period of 

 winter, and then, with the return of warmer weather, spreads out to 

 reoccupy the full range. 



There are many species, including the tree sparrow, slate-colored 

 junco, and Lapland longspur, that nest in Canada and winter in the 

 United States; while others, including the vesper sparrow, chipping 

 sparrow, grackles, red-winged blackbirds, bluebirds, the woodcock, 

 and several species of ducks, nest in the northern United States and 

 move south for the winter to areas along the Gulf of Mexico. This list 

 includes the more hardy species, some individuals of which may linger 

 in protected places well within the reach of severe cold, as, for example, 

 Wilson's snipe or jacksnipe, which frequently is found during subzero 

 weather in parts of the Rocky Mountain region where warm springs 

 assure a food supply. More than 100 of our summer birds leave the 

 United States entirely and spend the winter in the West Indies, or in 

 Central America or South America. For example, the Cape May 

 warbler, which breeds from northern New England, northern Michi- 

 gan, and northern Minnesota, north to New Brunswick, Nova Scotia, 



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