Distance of Migration
“The length of the migration journey varies enormously. Some birds do not migrate at all. Many a Cardinal, Carolina Wren, and Bob-white rounds out its whole contented life within ten miles of its birthplace. Other birds, for instance, the Pine Warbler and the Black-headed Grosbeak, do not venture in winter south of the breeding range, so that with them fall migration is only a withdrawal from the northern and a concentration in the southern part of the summer home—the Warbler in about a fourth and the Grosbeak in less than an eighth of the summer area.
“The next variation is illustrated by the Robin, which occurs as a species in the middle districts of the United States throughout the year, in Canada only in summer, and along the Gulf of Mexico only in winter. Probably no individual Robin is a continuous resident in any section; but the Robin that nests, let us say, in southern Missouri will spend the winter near the Gulf, while his hardy Canada-bred cousin will be the winter tenant of the abandoned summer home of the southern bird.
“Most migrants entirely change their abode twice a year, and some of them travel immense distances. Of the land-birds, the common eastern Night Hawk seems to deserve the first place among those whose winter homes are widely distant from their breeding-grounds. Alaska and Patagonia, separated by 115 degrees of latitude, are the extremes of the summer and winter homes of the bird, and each spring many a Night Hawk travels the 5000 miles that lie between. But some of the shore-birds are still more inveterate voyagers. These cover from 6000 to 8000 miles each way, and appear to make travelling their chief occupation.