AMERICAN MERGANSER 353 



or more than offset, their direct effect on the former, (c) Where mer- 

 gansers take only game fish it is because no other fish are available. 

 In many such water areas the game fish, insufficiently preyed upon, 

 develop populations more dense than the available food and oxygen can 

 properly support, with the result that there are no large fish, but only 

 an abundance of runts. Relief is not to be expected from angling, for 

 the angler doesn't care to catch runts; the need is for more mergansers 

 to thin out the stock of game fish and so enable the survivors to develop 

 properly, (d) In some places at some times mergansers may be unduly 

 plentiful and may have such an adverse effect on game fish that there 

 is need of control measures, (e) One point to be kept in mind in evalu- 

 ating mergansers is that they are extensively used as human food along 

 the coast and in regions where pioneer conditions still prevail. 



"In summary it may be said that the ecomomic status of mergansers 

 and the treatment to be accorded them are local matters, to be decided 

 in each case only after a searching scientific study of the facts involved. 

 Artificial conditions, such as those in fish-rearing ponds, present special 

 problems, which are often most satisfactorily and economically solved 

 by proper screening. In cases where a real need for reducing the num- 

 bers of mergansers is found, all operations should be carried on within 

 the provisions of the statutes by which these birds are protected." 



Of the swimming and diving habits of this bird, Bent (1923) says: 

 "The American Merganser is a heavy-bodied bird and sometimes ex- 

 periences considerable difficulty in rising from the water; if the cir- 

 cumstances are not favorable, it has to patter along the surface for a 

 considerable distance; when flying off an island it often does the same 

 thing unless it gets a good start from some high place, so that it can 

 swoop downward. In swift water it has to rise downstream, as it can 

 make no headway against the current; but it generally prefers to fly 

 upstream if it can. . . . When well under way the flight of this species 

 is strong, swift, and direct; on its breeding grounds it usually flies low, 

 along the courses of rivers or about the shores of lakes, seldom rising 

 above the tree tops; but on its migrations it flies in small flocks, high in 

 the air, with great velocity. . . . This sheldrake is probably the most 

 expert diver of its tribe, being built somewhat like a loon and approach- 

 ing it in aquatic ability. It can sink quietly down into the water like a 

 grebe or dive quickly with a forward curving plunge, clearing the water 

 for a foot or more as it does so. It swims swiftly on the surface, but 

 can attain even higher speed below it, where few fish can escape it. ... 

 The rapidity with which this species can dive from the air is remarkable. 

 While in full flight it plunges into the water, swims below the surface 

 for a distance and then suddenly emerges and continues its flight." 



Of its behavior on land, Millais (1913) says: "The walk is very 

 heavy and rolling, and the feet are placed on the ground deliberately 

 whilst the bill is pointed downward, and each step taken as if the bird 

 was afraid of tripping or falling. They seldom go more than a yard or 

 two from the water's edge, but run quite swiftly for a few yards if sud- 



