The Migration of North American Birds (1935)

For half a century the Biological Survey has been collecting data on the interesting and important phenomenon of the migration of North American birds. The field men of the Bureau have gathered information concerning the distribution and seasonal movements of the different species in many extended areas, from the Arctic coast south to the pampas of Argentina. Supplementing these investigations is the work of hundreds of volunteer ornithologists and bird students throughout the United States and Canada, who each year, spring and fall, forward to the Bureau reports on migrations observed in their respective localities. Added, to the mass of data thus assembled is a rapidly growing file of records of birds that have been banded and of the subsequent recovery of the marked individuals.