10 CIRCULAR 3 4 2, U. S. DEPARTMENT OE AGRICULTURE 



WATERFOWL POPULATIONS OF THE FLYWAYS. 



As stated above, there appears to be a readily demonstrable natural 

 law to the effect that, although groups of birds of the same species 

 may share a common breeding ground, they are so strongly influ- 

 enced by their ancestral lanes of migration that they will continue 

 to follow them even though conditions en route or on the wintering 

 grounds may become distinctly adverse to their welfare. As a work- 

 ing hypothesis, this was pointed out to ornithologists by the writer 

 6 or 7 years ago at a time when a severe outbreak of botulism was 

 decimating the ducks of western areas. At that time it was pre- 

 dicted that, because of the great attachment of migratory birds for 

 their ancestral flyways, it would be possible practically to extermi- 

 nate the ducks of the West without seriously interfering with the 

 supply of birds of the same species in the Atlantic and Mississippi 

 flyways, and that the birds of these species using the eastern flyways 

 would be slow to overflow and repopulate the devastated areas of the 

 West, even though environmental conditions might be so altered as 

 to be entirely favorable. 



The banding work has furnished abundant proof that ducks adhere 

 to their ancestral flyways. For example : At the waterfowl-banding 

 station at Lake Merritt, in Oakland, Calif., several hundred ducks 

 (chiefly pintails and baldpates, or widgeons) have been banded every 

 year since 1926. More than 550 return records have been received, 

 of which nearly 97 percent represent ducks that were taken within 

 the territory of the Pacific flyway. During the season 1933-34, more 

 than half the birds trapped at the station were already carrying 

 bands attached there in previous years. 



Of 243 return records of ducks banded in Saskatchewan, only 5 

 or 6 of these birds were killed at points outside the Central and 

 Mississippi flyways. Only two went to California and none to any 

 other Pacific coast State. 



Data from other stations show similar conditions. The nearest 

 approach to an exception is shown by records of ducks banded in 

 Kansas. The distribution of returns from these ducks covers a 

 greater scope of country than from any other group, as the birds 

 have been recovered at points scattered from the Atlantic to the 

 Pacific and from the sub-Arctic regions of Alaska and northwestern 

 Canada south through Mexico to Honduras and Colombia. Never- 

 theless, the gross total of all ducks banded in Kansas and recovered 

 at points outside the Central flyway is only about 15 percent of the 

 total number of return records received. 



In order to test the strength of the homing instinct and the attach- 

 ment of ducks to ancestral flyways, several shipments of banded 

 birds, chiefly pintails, were made from Avery Island, La., to pre- 

 arranged points, where in spring they were liberated in favorable 

 areas. During the season 1933-34 there were retrappecl at Avery 

 Island banded pintails that in previous seasons had been trapped 

 there, shipped by express, and liberated at Washington, D. C. ; Black- 

 water Migratory Bird Refuge, Cambridge, Md. ; the O. L. Austin 

 Ornithological Research Station, at North Eastham, Cape Cod, 

 Mass. ; Berkeley, Calif. : Lake Malheur Migrator} 7 Bird Refuge, 

 Voltage, Oreg. ; and the National Bison Range, Moiese, Mont. Here 



