134 DAVENPORT ACADEMY OF SCIENCES. 



discussion of the food habits will usualh- be placed under the 

 heading of the order or family. 



MIGRATION. 



The proper study of migration requires voluminous data from 

 many observers, extending over long periods. The position of the 

 State of Iowa, between the two great channels of migration for 

 the interior of the United States, affords unequaled opportunities 

 for such work. The data which has been received in this branch 

 has been too scanty and isolated to warrant more than general 

 statements of the times of appearance and departure. 



The Biological Survey of the United States Department of Agri- 

 culture has for nearl}- twenty years been accumulating data on 

 the migration of birds, receiving reports in the spring and fall of 

 each year from hundreds of observers. The Yearbook of the 

 Department of Agriculture for 1903, pp. 371-386, "Some New 

 .Facts About the Migration of Birds," by Wells W. Cooke, Assist- 

 ant, Biological Survey, contains the following statement: 



"For more than two thousand years the phenomena of bird 

 migration have been noted, but while the extent and course of the 

 routes traveled have of late become better known, no conclusive 

 answer has been fonnd to the question, why do birds migrate? ... 

 The broad statement can be made that the beginnings of migration 

 ages ago were intimately connected with periodic changes in the 

 food supply, but this motive is at present so intermingled with 

 others unknown, or but imperfectly known, that the migration 

 movements seem now to bear little relation to the abundance or 

 ab.sence of food. . . ^. Data recently collected at the Florida 

 light-houses by the Biological Survey show that .southward migra- 

 tion begins at least by the loth, and probably by the ist of July, 

 insect-eating birds departing when their food supplies are most 

 plentiful, and seed-eaters just before the heyday of harvest." 



It is undoubtedly true that many birds return to the far north 

 during the breeding season in order to find undisturbed solitude 

 during the season of incubation and moulting. The northward 

 retreat of the ducks and geese which nested commonly in Iowa 

 before its settlement, tends to confirm this. On the other hand, 

 many common birds return to breed in thickly populated locali- 

 ties here, leaving southern points which would apparently supply 

 greater seclusion and an equal food supply. 



