OUR GREATEST TRAVELERS 
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. 
THE BOBOLINKS ARE SEEKING 
ROUTES 
NEW 
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 Breton Island to Saskatchewan, 
2,300 miles, and the migration lines con- 
verge toward the rice fields of the South, 
195 
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 off from the western 
United States by the intervening arid 
region. But 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 map, and the probability 
is that the not distant future will see 
a large increase in these trans-Rock\ 
Mountain bobolinks. 
