34 A NATURAL HISTORY OF THE DUCKS 



good and bad breeding years, and destructive industries, as well as irruptions of 

 bird enemies. We need more studies like that conducted by Wetmore in the Bear 

 River marshes of Utah, where an estimate of the exact number of breeding pairs was 

 arrived at. Our own Biological Survey is doing as much of this sort of work as it can. 

 Now, there are reasons why the status of a given species is hard to get at, and most 

 of these reasons are not considered by the average sportsman. A census of particu- 

 larly attractive areas, where duck population gathers to the full limit of food re- 

 sources, is obviously misleading, for less favorable stopping-places will be drained 

 before the great resorts become affected. It might be likened to the depopulation of 

 some of our Western States, which does not in the least affect the city of New York. 

 Besides, migration routes are not hard and fast, and we are at a loss to explain the 

 irruptions of certain species at certain places, or their dearth at others. And then 

 there are droughts and floods, bad breeding years, destruction of great brackish- 

 water lagoons by breaking of beaches, introduction of carp or pike, and perhaps 

 catastrophes from storm and frost that we cannot possibly take into consideration. 

 The great northern periodic cycles of mice and rabbits with their attendant increase 

 of predaceous lynxes, hawks, and owls may even affect the breeding grounds of 

 ducks. And last, but not least, we want to know the approximate numbers destroyed 

 by man from the Arctic Ocean to the Gulf of Mexico, the decrease of breeding area 

 from time to time, and the effect of industries which may pollute the waters by 

 chemicals or scatter oils on the surface. 



Mr. E. W. Nelson, the present Chief of the United States Biological Survey, writes 

 me that he considers the molestation of wild-fowl by aeroplanes one of the most seri- 

 ous dangers for the future. They certainly have the effect of driving ducks entirely 

 away from regions over which they patrol, but duck are very adaptable, and I have 

 noticed that the Scaup Ducks on Lake Worth in Florida no longer pay any attention 

 to them. 



During the ornithological history of this country only one species of North Ameri- 

 can duck has disappeared, namely, the Labrador Duck. Whether this was due to 

 complete destruction upon some restricted breeding ground, or whether changes in 

 the molluscan fauna of our bays or harbors interfered with a delicately adjusted 

 dietary, which the specialized bill suggests, or whether it was from some entirely 

 unthought-of reason, we can only speculate. 



We must record the fact that Dresser's Eider is in great danger, unless the depre- 

 dations of the Newfoundland and Labrador fishermen can be stopped, but no other 

 species is in immediate danger here. 



Among factors which are of local importance in destroying ducks, we ought to 

 mention the accidental taking of large numbers of several species of diving ducks in 

 fish-nets. This has assumed some importance on Lake Erie. 



Nearly all species were on the down grade in America before spring shooting was 



