- BULLETIN 862, U. S. DEPARTMENT OF AGRICULTURE. 
VEGETABLE Foon. 
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 grain, 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 
maritima), 20 horned pondweed (Zannichellia palustris), 17 bushy 
pondweed (Najas flexilis), 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 gadwal! taken in Texas 
in November contained a mass of the foliage of small pondweed 
(Potamogeton pusillus) 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, inciuding 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 (S. 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, Loujsiana, had been feeding during 
