. H).CTOBER, 1902. 
THE MIGRATION OF BIRDS. 
1Q7 
. district of an individual to its winter home. These paths consist 
=- of coast Hnes, river valleys, mountain ranges and island chains. 
To illustrate, a bird may start somewhere near the Alleghany 
Mountains, follow a course along the Appalachian System to any 
one of the streams originating at its southern extremity, follow 
r this to the coast and the coast to some point in Florida or the 
' West Indies. Others might start somewhere along the tributaries 
; of the Potomac or the Hudson River or the Merrimac, and then 
- down the coast. 
Whereas, we have single birds and small groups starting from 
wholly different places, many will be brought together over the 
- same course; a number of such courses lead to larger ones, until 
i-we finally arrive at a physiographic area that is thronged with 
" migrants. Such an area is known as a migratory highway. 
It is quite generally accepted that the principal highways of 
' North America are the Atlantic Coast, the Appalachian Moun- 
tain System, the Mississippi River Valley, the Rocky Mountain 
I System, the Pacific Coast and an island chain extending across 
Cuba from Florida to Yucatan. 
Topographic features of less extent may be considered tribu- 
tary highways, or main highways for local areas^ The Great 
Lakes of North America ofifer some peculiar conditions in the 
migrations of those birds that spend the summer north of them 
and the winter in the south. At the Straits of Mackinac we have 
a narrow neck where the land to the north and south of the Lakes 
is not separated by considerable areas of water. We have here a 
mere point in the geography of North America toward which in- 
numerable birds converge in their flight from one side of the Lakes 
to the other. At Spectacle Reef light-house, which lies just east 
of the entrance into the straits, there have been upwards of four 
. and five hundred birds killed in one night by flying against the 
. tower. 
How in general the topographic features of a district influence 
. lines of migration is well known to all bird students. A careful 
. study of the data presented in Prof. Cooke's Report on Migration 
' in the Mississippi Valley shows, as we should expect, that birds 
■ resident in Wisconsin use the Mississippi River as a highway 
(41). Furthermore, after following this river north to the mouth 
of the Rock River, it is a noteworhy fact that immense numbers 
of our birds enter the state along a course following the Rock 
f 41. Gooke: Eeport on Bird Migration in Miss. Vallev. U. S. Dept. 
Agr. Bull., No. 2, 1888. 
