OUR GREATEST TRAVELERS 



195 



a day for the next 20 days, while it is 

 rounding the western end of the Gulf of 

 Mexico. It more than doubles this rate 

 while passing up the Mississippi and 

 Ohio rivers. The crossing of the Alle- 

 ghany Mountains comes next, and there 

 are only 200 miles of progress to show 

 for the 10 days of migration. By this 

 time spring has really come east of the 

 Alleghanies, and the swallow travels 60 

 miles a day to its summer home in Nova 

 Scotia. 



It is to be noted that the swallow, like 

 the robin and the black-poll warbler, 

 works up to high rates of speed when it 

 is traveling on a diagonal, and that except 

 during the 10 days spent in crossing the 

 mountains, each 10 days' travel covers 

 approximately five degrees of latitude. 



SOME NARROW MIGRATION ROUTES 



The accompanying illustration of the 

 range of the scarlet tanager (page 194) 

 is given to show the narrowness of the 

 migration route as compared with the 

 width of the summer and winter homes. 

 This tanager nests from New Brunswick 

 to Saskatchewan, a region extending over 

 1,900 miles of longitude. The Missis- 

 sippi Valley birds go south and the New 

 England birds southeast, until they all 

 leave the United States along 800 miles 

 of Gulf coast from Texas to Florida. 

 The migration lines continue to converge 

 until in southern Central America they 

 are not more than a hundred miles apart. 

 Arrived in South America for the win- 

 ter, the birds scatter over a district about 

 one-half the area of the summer home, 

 with an extreme east-and-west range of 

 about 700 miles. 



TIIK ROnOLIXKS ARE SEEKING NEW 

 ROUTES 



The migration route of the bobolink 

 (page 194) shows a similar though not 

 so decided a contraction at its narrowest 

 part. The summer home extends from 

 Cape lireton Island to Saskatchewan. 

 2,300 miles, and the migration lines con- 

 verge toward the rice fields of the South, 



the objective point of all bobolinks, no 

 matter where they nest. 



Having gorged themselves to repletion, 

 they press on toward their Brazilian win- 

 ter abode ; but the South Carolina and 

 Georgia birds take a course almost at 

 right angles to that chosen by the scarlet 

 tanagers from those States, and strike 

 out directly across the West Indies for 

 South America. In this part of their 

 journey their migration path contracts, 

 to an east-and-west breadth of about 800 

 miles, while a very large proportion of 

 the birds restrict themselves to the east- 

 ern 400 miles of this route. In South 

 America the region occupied during the 

 winter has about one-fifth the breadth 

 and one-third the area of the breeding 

 range. 



The bobolinks of New England have 

 witnessed great numerical changes, or 

 evolutions. When the white man arrived 

 on the scene, nearly all of New England 

 was covered by primeval forest and bob- 

 olink meadows were scarce. As the for- 

 est gave place to hay-fields, the bobolinks 

 promptly took advantage of their chance 

 and their numbers increased steadily until 

 the maximum was reached some 40 years 

 ago. Then the newly invented mowing 

 machine and the horsepower hay-rake 

 began to destroy thousands of nests and 

 caused a marked diminution in the bobo- 

 link census. 



The case of the bobolink is a fitting 

 close to this article, because it is reveal- 

 ing to us at the present time the manner 

 of evolution of a new migration route. 

 By nature a lover of damp meadows, it 

 was formerly cut ofif from the western 

 L'nited States by the intervening arid 

 region. lUit with the advent of irriga- 

 tion and the bringing of large areas 

 under cultivation, little colonies of nest- 

 ing bobolinks are beginning to appear 

 here and there almost to the Pacific. 

 Some of them are shown by dots on the 

 accompanying maj). and the i)robabiliiy 

 is that the not distant future will see 

 a large increase in these trans-Rocky 

 Mt)untain bobolinks. 



