ROUTES OF MIGRATION 45 
highway of migration which crosses the southern Alleghanies from 
northwest to southeast. This is evidently followed by Kirtland’s 
Warbler, which nests in northern Michigan and winters in the Bahamas, 
and it brings to our southeast Atlantic Coast, with more or less regular- 
ity, birds which are practically unknown in our North Atlantic States. 
pl era, Mutt A etoactarnh eee ae tioonan te Went Ladies 
Mexico and Central America. : : ; 
Dotted area—Breeding range. Black area—Winter range. Arrows—Migration 
route. 
There are also minor routes or paths of migration formed, generally, 
by favorable local conditions, but in some instances difficult to explain. 
T have seen Tree Swallows, in the spring, on the Gulf coast of Florida, 
migrating northward low over the great expanse of unbroken marshes, 
but evidently following a definite track. The scattered flocks were 
often separated by several miles, but each one followed in the wake of 
its invisible predecessor as though guided by the marks of wing- 
beats in the air. 
