6 BULLETIN 720, U. S. DEPARTMENT OF AGRICULTURE. 
mallards frequenting their home. The former were found in about 
300 of the mallard stomachs examined, and there were thousands in 
some of them. Coontail was found in 669 stomachs. The leaves of 
the plant as well as the seeds are eaten. The largest number of seeds 
found in any one gizzard was 150. 
WILD CELERY AND ITS ALLIES (4.26 PER CENT). 
Wild celery (Vallisneria spiralis) is well known for its value as a 
wild-duck food. It is most important to the diving ducks, which 
are able to feed on the rootstocks and buds, but shoalwater ducks 
occasionally obtain these parts of the plant.and in the proper season 
can feed at will on the leaves. Thirty-eight of the mallards exam- 
ined had fed on wild celery and 135 upon the seeds of a related plant, 
frogbit (Limnobium spongia). Another plant of the same family, 
waterweed (Philotria), was found in small quantity im only two 
stomachs. | 
WAPATO AND ITS ALLIES (3.54 PER CENT). 
Wapato belongs to the family of arrowheads, many of which have 
large and nutritious tubers. The mallard is not particularly adapted 
to get food requiring such strenuous digging, but nevertheless man- 
ages to obtain a share of the coveted, tubers where they are abun- 
dant. From 6 to 8 tubers of the delta potato (Sagittaria platyphylla) 
were taken at a single meal by some of the birds, as were no fewer 
than 11 tubers of another species of Sagittaria. Tubers, stems, and 
seeds of Sagittaria were found in more than a hundred stomachs, 
and seeds of the related water plantain (Alisma) in three. 
SEEDS OF TREES AND SHRUBS. 
Where trees and shrubs bearing nutritious fruits are so situated 
that their products fall into the water, they sometimes become an 
important source of wild-duck food. Those most important to the 
mallard are trees of the elm and oak families. The water elm 
(Planera aquatica), a common tree of southern swamps, has large 
nutritious seeds which remain for months in a pertect state of pres- 
ervation in the water into which they fall. There they are found 
and eagerly devoured by wild ducks. One hundred and fifty-nine of 
the mallards examined had fed upon these seeds, no fewer than 200 
of them being taken by a single duck. The seeds of hackberry 
(Celtis), a tree also of the elm family, were found in 46 stomachs; 
and altogether seeds of plants of this family com poss 4.11 per cent 
of the total food of the mallards examined. 
The next largest item of mallard food produced by trees is acorns. 
These were found in 37 stomachs and form 2.34 per cent of the whole 
subsistence. Mallards sometimes resort in flocks to woods where 
