364 



THE NATIONAL GEOGRAPHIC MAGAZINE 



By the first of May he arrives in central 

 Missouri, which the robins left 60 days 

 earlier, and yet he reaches northwestern 

 Alaska only 10 days later than the robins. 

 The latters' 90-day schedule has been 

 shortened by the warbler to 30 days. 



The black-poll warbler furnishes a 

 striking example of speed acceleration 

 during the latter part of migration. As 

 indicated on the map of his migration 

 route (page 348), between April 20 and 

 April 30 he goes from central Missouri 

 to central Iowa, a distance of 300 miles, 

 or an average of 30 miles a day. The 

 next 10 days the rate rises to 100 miles 

 a day, while during the last few days of 

 migration a velocity of 300 miles a day 

 is attained. 



In contrast, notice the dates, distances, 

 and speeds indicated for the cliff swal- 

 low on its migration-route map ( page 

 349 ) . The swallow must strike out for 

 the north very early, since by March 10 

 it is already 2,500 miles from the winter 

 home, and yet is averaging only 25 miles 

 a day for the next 20 davs, 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 cross- 

 ing the mountains, each 10 days' travel 

 covers approximately five degrees of lati- 

 tude. 



SOME NARROW MIGRATION ROUTES 



The accompanying illustration of the 

 range of the scarlet tanager (page 363) 

 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. 



THE BOBOUNKS ARE SEEKING NEW 

 ROUTES 



The migration route of the bobolink 

 (page 365) shows a similar though not 

 so decided a contraction at its narrowest 

 part. The summer home extends from 

 Cape Breton 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 



