34 BIRDS OF SOUTH DAKOTA 
BIRD MIGRATION 
We who live in the Northern Hemisphere are peculiarly 
fortunate in the privilege we have of viewing a bird procession 
twice a year that spreads over the whole of North America to 
nest. Mr. Wells W. Cooke says, “South America has almost no 
migratory land birds, for bleak Patagonia and Tierra del Fuego 
offer no inducements to these dwellers of the limitless forests 
of the Amazon.” (Department of Agriculture, Bulletin No. 
185, p. 4.) 
There are four classes of birds with respect to migration: 
(1) permanent residents ; those that do not migrate; (2) summer 
residents; those that come to us from the south in spring and 
return in the autumn; (3) winter residents; those that come to 
us from the north in the autumn and return in spring; (4) tran- 
sients, or migrants; those that pass through our State on their 
way north in spring and again when they return south in au- 
tumn. 
The general direction of bird migration is north and 
south, but with many species this direction may swing at times 
to east and west. Many Snipes and Plovers, for example, which 
spend the winter in South America, come north across the Gulf 
of Mexico, then up the Mississippi Valley, and nest in the in- 
terior of North America. In the autumn they take an easterly 
course to the Atlantic coast, thence south to their wintering 
place. The Bobolinks that nest in the northwest go to their win- 
ter home in South America by the roundabout way of Florida, 
and the Connecticut Warblers come north through the interior 
of the United States and return south along the Atlantic coast. 
The reason for these circuitous routes is not well under- 
stood. Generally speaking, birds migrating follow “mountain 
chains, coast lines and particularly river valleys,’ but there are 
so many exceptions that other causes evidently enter into the 
problem. At present in South Dakota many birds are extending 
their range westward with the growth of trees. These birds will 
follow the migrating routes by which they come, returning 
first east and then south. Many birds follow such a route be- 
cause their range has been extended in this way. 
