Waterjowl 



205 



TABLE 42. Composition of breeding populations 



Locality 



One cannot dismiss this fact as unalterable because these grounds are "too 

 far South." In the West, since the cessation of spring shooting, mallards and 

 other species have nested freely almost to the Mexican border. 



In southern Illinois there is a tradition among rivermen that mallard decoys 

 cannot be propagated in the bottoms that they must be moved to the uplands, 

 otherwise the ducklings will riot survive. This sounds like some insect-borne 

 juvenile disease. O'Roke, of the Michigan School of Conservation, is finding that 

 survival of mallard ducklings in that State is affected by a juvenile disease carried 

 by the black-fly. La Rue finds the survival of Michigan herring gulls affected by 

 a parasite fatal to juveniles and carried by perch. It is predicted that many water- 

 fowl breeding ranges will ultimately be found to be determined by particular 

 juvenile diseases and parasites, some of which may be subject to control. Here is 

 another virgin field for science to come to the aid of conservation. 



By and large, the cumulative shrinkage in breeding grounds cannot, however, 

 be reversed, either by more science, or by more appropriations for public acquisi- 

 tion. The only fundamental remedy is to recognize the fact that undrained un- 

 grazed private marshlands perform a public service in producing migratory birds, 

 and to give the owner an incentive for keeping, continuing, or restoring that serv- 

 ice by according them a preferential tax status, such as is now accorded in some 

 States to private forests, on the same principle of public service. The public can 

 never acquire enough of the small marshes to offset the ones which are being 

 taxed out of existence, nor can science show how to grow ducklings in a corn- 

 field. The steam-roller of economic self-interest must somehow be steered so 

 that it will work with, not against, the feeble palliatives so far employed to avert 

 that spiritual calamity a duckless America. 



Refuges and Restgrounds. Baiting is not the only reason for the con- 

 centration of waterfowl on the lower Illinois. The accidental existence of large 



