12 BULLETIN 720, U. S. DEPARTMENT OF AGRICULTURE. 
wild celery. The pondweed group alone, including the ordinary 
pondweeds (Potamogeton), bushy pondweed (Navas), widgeon-grass 
(Ruppia), horned pondweed (Zannichellia), and eelgrass (Zostera), 
composed 32.34 per cent of the total diet. Leaves, stems, tubers, 
winter buds, and seeds of pondweeds are eaten, and 700 seeds were 
found in a single stomach. No fewer than 4,000 seeds of eelgrass 
were taken from the gizzard and gullet of one black duck. Wud 
celery is an important food plant, but as it was not tabulated sepa- 
rately, its percentage can not be stated. 
Following the pondweed group in importance are the grasses and 
sedges, each contributing nearly 11 per cent to the diet of the black 
mallard. The most important grasses are salt-marsh grass (Spar- 
tina) and wild rice (Zizania). Some stomachs contained from 1,000 
to 1,200 grains of wild rice. Cultivated rice was found in two giz- 
zards, to the extent of 720 kernels in one. It was gleaned from 
fields already harvested. A notable part of the total percentage of 
grasses was made up of corn supplied to the ducks as bait. One 
bird had taken 227 kernels at a meal. Wheat, also used as a bait, 
was found in one stomach. 
The -sedges which supply most food to black ducks are the bul- 
rushes (Scirpus). Mainly the seeds of these plants are devoured, and 
2,000 have been found in one stomach. The tubers, as a rule, are 
sparingly eaten, but one species (Scirpus pauciflorus), common about 
the southern end of Hudson Bay, has a tender propagating bud 
which is eagerly eaten by ducks, and of which the black duck takes 
its share. Of other sedges, the following total numbers of seeds were 
taken from single stomachs: Oarex, 320; twig rush (Oladium), 720; 
and Fimbristylis, 900. The stems, leaves, and rootstocks of sedges 
also are eaten occasionally. 
Smartweeds are important to the black duck as fale they are to 
many other wild fowl. Their seeds make up a twentieth of the food 
of this bird, and nine different species were identified; from 2,000 to 
3,200 were found in individual stomachs, and in one the enormous 
total of 36,300. 
Seeds of bur reeds (Sparganium), usually not a conspicuous ele- 
ment of wild-duck food, were found in 144 stomachs of black ducks, 
to the number of 200 to 250 in several. They make up 3.37 per cent 
of the diet. Algz form a larger element of the food of the black duck 
than of most of its relatives. This is merely because the maritime 
habits of the bird give it access to seaweeds. Musk grasses (Chara), a 
fresh-water group, also were among the alge eaten. 
Other items of vegetable food worthy of mention are the seeds of 
water shield (Brasenia), waterlilies, and coontail (Ceratophyllum), 
which together form 1.36 per cent of the food; leaves, roots, and 
tubers of various wapatos; seeds of pickerel weed, and of grape and 
