4 BULLETIN 862, IT. S. DEPARTMENT OF AGRICULTURE. 



Vegetable Food. 



As computed from the contents of 362 stomachs collected during 

 the six months from September to March, 97.85 per cent of the food 

 of the gadwall consists of vegetable matter. This is made up as 

 follows: Pondweeds, 42.33 per cent; sedges, 19.91; algae, 10.41; 

 coontail, 7.82; grasses, 7.59; arrowheads, 3.25; rice and other culti- 

 vated gram, 1.31; duckweeds, 0.61; smartweeds, 0.59; wild celery 

 and waterweed, 0.53; waterlilies, 0.52; madder family, 0.37; and 

 miscellaneous, 2.61 per cent. 



PONDWEEDS (nAIADACEAE), 42.33 PER CENT. 



Of the 417 gadwalls whose stomachs were examined, 155 had 

 eaten true pondweeds (Potamogeton spp.), 112 widgeon grass (Ruppia 

 maritime,), 20 horned pondweed (ZannicheUia palustris), 17 bushy 

 pondweed (Najas jiexilis), 3 eelgrass (Zostera marina), and 8 pond- 

 weeds which were too far advanced in the process of digestion to be 

 further identified. In nearly all cases the pondweed food consisted 

 chiefly of leaves and stems, and sometimes buds and tubers. Seeds 

 were often present, sometimes in considerable numbers, but as a rule 

 they appeared to be merely incidental. Pondweeds are undoubtedly 

 the favorite food of this species, as well as of the baldpate, and they 

 are eaten very greedily. The gullet of one gadwall taken in Texas 

 in November contained a mass of the foliage of small pondweed 

 (Potamogeton pusiUus) the size of a billiard ball. A series of 26 

 stomachs taken in North Carolina in December contained practically 

 nothing but the leaves and stems of pondweeds, including true pond- 

 weeds, bushy pondweed, and widgeon grass. Many of these stomachs 

 were crammed. Often a few of the seeds were present, and three 

 stomachs contained in addition a few sedge seeds. Other rather 

 large series of gizzards containing chiefly foliage of pondweeds were 

 taken in Florida, Louisiana, Utah, and North Dakota. 



SEDGES (CYPERACEAE), 19.91 PER CENT. 



The sedges, second in favor among the food items of the gadwall, 

 constitute an important exception to this bird's rule of feeding upon 

 the leaves and stems of plants rather than upon the seeds, for the 

 leaves and stems of practically all the sedges are coarse, fibrous, or 

 even woody, and do not make choice morsels. On the other hand, 

 the seeds are a favorite item of food among most fresh-water ducks. 

 The sedge seeds most often eaten by the gadwall were those of three- 

 square (Scirpus americanus) , by 150 birds; prairie bulrush. (S. palu- 

 dosus), by 27; salt-marsh bulrush (#. robustus), by 24; unidentified 

 bulrushes (Scirpus spp.), by 47; saw grass (Cladium effusum) , by 68; 

 and chufas (Cyperus spp.), by 31. A considerable number of birds 

 from the Mississippi Delta, Louisiana, had been feeding during 



