. Bulletin. Natural history; Natural history. Fig. 11.—Water-hemp or pigweed {Acnida altissima). This plant grows well on mud flats. mud flats, ditchbanks, and similar areas, is a good source of duck food in seasons favorable to its growth. It ranked eighth in the occurrence-percentage index, table 37. This plant is subject to poor seed yields when growing conditions are un- favorable, such as occurred in 1938 and 1939. In those years, it was represented in only about 1 per cent of the total or- ganic contents of the duck gizzards exam- ined, but in 1940, a year in which beds were abundant and
. Bulletin. Natural history; Natural history. Fig. 11.—Water-hemp or pigweed {Acnida altissima). This plant grows well on mud flats. mud flats, ditchbanks, and similar areas, is a good source of duck food in seasons favorable to its growth. It ranked eighth in the occurrence-percentage index, table 37. This plant is subject to poor seed yields when growing conditions are un- favorable, such as occurred in 1938 and 1939. In those years, it was represented in only about 1 per cent of the total or- ganic contents of the duck gizzards exam- ined, but in 1940, a year in which beds were abundant and luxuriant, its volume increased to per cent. The puddle ducks, especially the mallard, pintail, and both teals, used this plant. It was not un- common to find 40,000 seeds in a mallard gizzard, or 25,000 to 30,000 in a pintail or teal gizzard. Only the seeds and seed heads of this plant were used. Water-hemp seeds or seed heads, found in 695 gizzards, table 38, made up per cent of the total organic contents of all gizzards included in this study. Appar- ently, the usage of this food plant through- out the fall changed little as long as the seeds were accessible. An early freeze would probably have lessened its use, but the 1938-1940 study did not indicate any decrease in percentage of use as the season progressed. Water-hemp can be consid- ered a good all-fall food for most species of dabbling ducks. Nodding Smartweed Poly go n u m I a path if oliu in Nodding smartweed, fig. 12, grew abun- dantly along the margins of most Illinois rivers and bottomland lakes in 1938- 1940. Gizzard analyses showed that most of the important species of waterfowl fed on the seeds in significant amounts. Seed, produced in abundance, seemed to serve principally as a supplemental food, as it never constituted a complete feeding. Seeds of nodding smartweed, present in 1,145 gizzards, table 38, constituted per cent of the total organic contents of all gizzards examined. The period of.
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