36 CICULAR 363, U.S. DEPARTMENT OF AGRICULTURE 
fair regularity east to the western shore of Lake Michigan, and west 
to the foothills of the Rocky Mountains, but the great bulk of the 
species moves north and south through a relatively narrow path in 
the central part of the continent. Present knowledge suggests that 
the reason for this narrow migration range is the close association that 
Harris’s sparrow maintains with a certain type of habitat, including 
brushy places, thickets, edges of groves, and weed patches. While 
these environmental conditions are found in other parts of the country, 
the region crossed by this sparrow presents almost a continuous suc- 
cession of habitat of this type. Its winter range extends from south- 
Let Ve 
TARA Lai? 
WSS BR FE DING RANGE 
YM Win TER HOME 
eo FASTEAND WEST: EIMiteSoe 
OF MIGRATION ROUTE 
B4502M 
FIGURE 17.—Distribution and migration of the scarlet tanager. During the breeding season individual 
scarlet tanagers may be 1,900 miles apart in an east-and-west line across the breeding range. In migra- 
tion, however, the lines converge until in southern Central America they are not more than 100 miles 
apart. For migration paths of other widths see figures 16, 18, and 19. 
eastern Nebraska and northwestern Missouri, across eastern Kansas 
and Oklahoma and through a narrow section of central Texas, at 
places hardly more than 150 miles wide. 
The scarlet tanager presents another extreme case of narrowness of 
migration route (fig. 17), its breeding range extending in greatest 
width from New Brunswick to Saskatchewan, a distance of about 
1,900 miles. As the birds move southward in fall their path of migra- 
tion becomes more and more constricted, until at the time they leave 
the United States all are included in the 600-mile belt from eastern 
Texas to the Florida peninsula. Continuing to converge through 
Honduras and Costa Rica, the boundaries there are not more than 
