196 BULLETIN 126, UNITED STATES NATIONAL MUSEUM. 



In California the canvasback partakes of more animal food, for wild celery dots 

 not grow in this State. On the shallow water of the tidelands and marshes it feeds 

 extensively on crustaceans and shellfish, thereby acquiring a "fishy " taste and thus 

 becoming undesirable as a table bird. The stomachs of some canvasbacks collected 

 on San Pablo Bay contained clams (Mya arenaria), and snails {Odostomia, species); 

 one stomach from Tia Juana Slough, near San Diego, contained periwinkles {Cerithi- 

 dea calif ornica), and another from the same place contained grass blades, stems, and 

 roots. A stomach from Guadalupe, San Luis Obispo County, was filled with barley, 

 there being 22 whole kernels and many hulls; but there is a possibility that this was 

 bait put out by hunters. 



In connection with the feeding habits of the canvasback it may 

 be well to call attention to an interesting case of lead poisoning in 

 this species, resulting from feeding on grounds which have been shot 

 over considerably. 



Mr. W. L. McAtee (1908) published the following account of it in 

 The Auk: 



Conditions similar to those described by Mr. J. H. Bowles for the Nisqually Flats, 

 Puget Sound, exist at Lake Surprise, Texas. To the latter locality canvasbacks re- 

 sort from November to March. About the 1st of January, each year, many of these 

 ducks are found among the rushes along the shore in various stages of sickness. Some 

 can dive, but can not fly, and all become emaciated. A part of these of course are 

 cripples, but most of them, although free from wounds, are plainly diseased, and ac- 

 cording to the belief of those who have had most experience with them, the cause is 

 lead poison from shot in the gizzards. No fewer than 40 shot have been taken from 

 a single gizzard and the shot generally bear evidence of more or less attrition. As the 

 season advances, the diseased ducks gradually disappear; the greater part die, but 

 some it is thought recover. According to the information at hand no other species 

 than the canvasback is thus affected at Lake Surprise. 



Ducks secure a great deal of their food by sifting mud through their bills; if shot 

 are abundant in mud, it is not hard to understand how the birds may collect a con- 

 siderable number in a day. Resisting digestion to a marked degree, as shot do, the 

 quantity in the gizzard is added to day by day, the ducks continuing to feed over 

 the same grounds, until finally the gizzard is clogged with shot, and malnutrition, if 

 not actual poisoning, ensues. Epidemics, such as we now have evidence of on Puget 

 Sound and at Lake Surprise, in all probability will increase in number, adding an- 

 other to the almost overwhelming array of unfavorable conditions against which our 

 ducks must more and more hopelessly struggle. 



Behavior. — The flight of the canvasback,. though apparently la- 

 bored, is really quite rapid, strong, and well sustained. When migrat- 

 ing or when flying to and from their feeding grounds they fly in wedge- 

 like flocks, usually at a considerable height and with more velocity 

 than is apparent. When on the wing the canvasback can be recog- 

 nised by the long, slender neck and head, carried in a downward curve, 

 by the long pointed bill and by the sharp-pointed wings; it is a longer 

 and more slender bird than the redhead; when sitting on the water it 

 can be distinguished from the redhead or the scaups, almost as far as 

 it can be seen, by the extreme whiteness of the back. 



The canvasback is essentially a diving duck and one of the most 

 expert at it; it swims low in the water like a grebe and dives quickly, 



