CANVAS-BACK 131 



The vegetable food of the entire series was divided as follows: water-lily family 

 19.49% including the banana water-lily and the sweet-scented water-lily (Castalia 

 odorata). The pond-weeds came next in order of abundance and made up 17.85% of 

 all the food. The sago pond-weed (Potamogeton pectinatus) found in 189 gizzards 

 proves this a very important item. One gizzard and crop contained 59 tubers, an- 

 other 57 and a third 52, while seeds were also taken in very large numbers. 



The arrow-head family, of which the delta duck-potato (Sagittaria platyphylla) 

 was the favorite, composed 15.7%. The frogbit family was taken to the extent of 

 10.8% and wild celery was the only member of this family, being present in forty 

 stomachs. The fact that so few stomachs contained this famous duck food may be 

 explained on the basis of the localities where the ducks were shot. 



Grasses, including wild rice and wild millet, formed 11.49%, sedges 2.94% and 

 algse, water milfoil, smart-weeds and other families in small amounts. 



The animal food, 15.15%, is larger than one would expect, but this is accounted for 

 by the abundance of a small snail in the stomachs from Louisiana, while ten other 

 species of snails were identified. Insects were, of course, present in small numbers 

 (1.46%) while accidental food such as scales and bones of fishes, a rat tooth and the 

 teeth of musk-rats were present in a few stomachs. 



Hollister (Kumlien and Hollister, 1903) remarks that the so-called celery buds 

 which he took from the crop of a Canvas-back in Wisconsin, and planted, turned out 

 to be not Vallisneria but one of the pond-weeds. The gemmae of this weed comprise 

 the greater part of the food in October and November on Lake Kushkonong. 



When frozen out of its usual feeding grounds the Canvas-back will live for a time 

 on Zostera and on crustaceans. 



In California, where there is no Vallisneria, the Canvas-back gets more animal food 

 than in the East, partaking extensively of crustaceans and shell-fish and acquiring a 

 fishy flavor. Stomachs from San Pablo Bay, California, contained clams {Mya 

 arenaria) and snails. One from near San Diego contained periwinkles (Cerithidea 

 calif arnica) ; another from the same place contained grass blades, stems and roots 

 (Grinnell, Bryant and Storer, 1918). 



Some unusual foods have been noticed by Audubon, who lists fishes, tadpoles, 

 water-lilies, leeches, snails, and mollusks among the foods found in their stomachs. 

 I hesitate to mention the disgusting habit to which this "king" of all the duck tribe 

 sometimes resorts. Together with other water-fowl it occasionally gorges itself on 

 decayed salmon in the bays of British Columbia and Washington (W. L. Dawson 

 and Bowles, 1909) . Wilson mentions their swarming about a wrecked ship which had 

 been loaded with wheat, at Egg Harbor, New Jersey. I was told a similar tale about 

 a wheat vessel which was wrecked on the beach at Long Point, Lake Erie, where a 

 good many of these ducks actually spent the winter living almost entirely on the 

 wheat. A stomach from California was found filled with barley (Grinnell, Bryant 

 and Storer, 1918). 



