some of the sparrows — the snow buntings, longspurs, juncos, and tree 

 sparrows. Other species, however, though they travel in flocks, main- 

 tain a very loose formation; examples are the turkey vultures, the 

 hawks, swifts, blue jays, swallows, warblers, and bluebirds. Still 

 others, the grebes, great horned owls, winter wrens, shrikes, and belted 

 kingfishers for example, ordinarily travel alone and when several are 

 found in close proximity it is an indication that they have been drawn 

 together by unusual conditions, such as abundant food. 



Where Birds Migrate 



Definite evidence shows that both the length and the duration of 

 the migratory journey vary greatly. The bobwhite and the western 

 quails, the cardinal, the Carolina wren, and probably some of the tit- 

 mice and woodpeckers, which are apparently almost or quite non- 

 migratory, may round out their full period of existence without at any 

 time going more than lo miles from the nest where they were hatched. 



Short and undetermined migrations 



Song sparrows, meadow larks, blue jays, and some other species 

 make such short migrations that the movement is difficult to detect, 

 as individuals may be found in one area throughout the year. Thus, 

 at the southern part of the range there is merely a concentration in 

 winter, the summer individuals being entirely sedentary. Speculation 

 is useless on the distances of individual migration without definite evi- 

 dence concerning the precise winter quarters of birds that summer in 

 a particular part of the breeding range of the species, but from the 

 records of banded birds important evidence is becoming available. 

 Eventually it may be possible to say definitely just how far the song 

 sparrows that nest in northern New England and the Maritime Prov- 

 inces of Canada travel to their winter quarters, and whether the blue 

 jays of New York and the upper Mississippi Valley remain throughout 

 the winter in their breeding areas, or move farther south and relinquish 

 their places to individuals from southern Canada. 



An illustration of what is now known on this subject is found in the 

 case of the robin. This bird occurs in the Middle Atlantic States 

 throughout the year, in Canada only in summer, and along the Gulf 

 coast only as a winter resident. On the Atlantic coast its movements 

 are readily ascertained, since, for example, in the section about Wash- 



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