12 BULLETIN 720, U. S. DEPARTMENT OF AGRICULTURE. 



wdld celery. The pondweed group alone, including the ordinary 

 pondweeds (Potamogeton), bushy pondweed (Naias), widgeon-grass 

 {Rwpfia), 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. Wild 

 celery is an important food plant, but as it was not tabulated sepa- 

 rately, its percentage can not be stated. 



Followmg 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 iMucifiorus) , 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: Car ex, 320; twig rush {Cladium), 720; 

 and Fimbristylis , 900. The stems, leaves, and rootstocks of sedges 

 also are eaten occasionally. 



Smartweeds are important to the black duck as also 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. iUgse 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 algse eaten. 



Other items of vegetable food worthy of mention are the seeds of 

 water shield (Brasenia), waterlilics, 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 



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