marsh bird would die of hunger on arriving in a very dry country.
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Fig. 317.—Cranes Migrating, with leader at point of V-shaped line.
The landmarks of the route are mountains, rivers, valleys, and coast lines. This knowledge is handed down from one generation to another. It includes the location of certain places on the route where food is plentiful and the birds can rest in security. Siebohm and others have studied the routes of migration in the Old World. The route from the nesting places in northern Europe to Africa follows the Rhine, the Lake of Geneva, the Rhone, whence some species follow the Italian and others the Spanish coast line to Africa. Birds choose the lowest mountain passes. The Old World martin travels every year from the North Cape to the Cape of Good Hope and back again! Another route has been traced from Egypt along the coast of Asia Minor, the Black Sea and Ural Mts. to Siberia.
Field Study of Migration.—Three columns may be filled on the blackboard in an unused corner, taking several months in spring or fall for the work. First column, birds that stay all the year. Second column, birds that come from the south and are seen in the summer only. Third column, birds that come from the north and are seen in winter only. Exact dates of arrival and departure and flight overhead should be recorded in notebooks. Many such records will enable American zoologists to trace the migration routes of our birds. Reports may be sent to the chief of the Biological Survey, Washington, D.C.
