DISTRIBUTION AND MIGRATION OF NORTH AMERICAN 



WARBLERS. 



INTRODUCTION. 



The warblers are birds of wide distribution. They occur in summer 

 in greater or less abundance over nearly the whole of North America 

 except the arid lands of the Southwest and the Barren Grounds of the 

 far North. Though of small size they are brightly colored, and 

 during the migrations they come in such numbers, both of species 

 and individuals, that they often form the most conspicuous part of a 

 bird wave, and their return is awaited with eagerness by students of 

 migration. In spring the lover of the beautiful finds among them 

 brilliant colors in multiple variety; the practiced ear is taxed to dis- 

 tinguish their faint songs dropping from the tree tops; and the experi- 

 enced ornithologist feels a pleasurable excitement in scanning each 

 individual of the passing host as he seeks the rarity that will more 

 than repay the time spent in the search. In the fall, when the same 

 bands in less conspicuous garb return with the season's offspring, even 

 the skilled observer finds himself perplexed to identify every species as 

 it passes — singly, by twos and threes, in restless flocks, or in the 

 swarming numbers of the bird wave. 



The family of warblers is a large one, its members in the United 

 States numbering over seventy species and subspecies. These, in the 

 distances they travel in migration and in the size of the areas they 

 occupy during the breeding season, present an enormous range of 

 variation. Some, as the yellow warbler {Dendroica sestiva) and the 

 yellow-breasted chat {Icteria viren^), breed over the greater part of 

 the United States, excepting the arid areas, and make long flights in 

 migration; while others, as the Belding yellowthroat {Geothlypis 

 heldingi), are restricted to areas only a few square miles in extent, 

 where they remain the year around. Among the birds that perform 

 regular migrations are some that go only a few miles, as the Florida 

 yellowthroats (Oeothlypis trichas ignota), that cross back and forth 

 between Cuba and the Gulf States, and others that travel many 

 thousands of miles, as the black -poll warblers {Dendroica striata) that 

 nest in Alaska and northern Canada and spend the winter in South 

 America, from Brazil to Chile. From the foregoing it is obvious 

 that the size of the area occupied in winter varies enormously— thus, 



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