May, 1943 
BELLROSE & ANDERSON: 
Gt 
Duck Foop PLANTS 42 
went oa Pe RHO ee 
Fig. 8.—Coontail (Ceratophyllum demersum) ranks below the moist-soil plants in value as 
a source of food for waterfowl, but leads the truly aquatic species. 
leaves and stems. 
Aug. 1 often fails to ripen before frost. 
On the other hand, this millet sown in 
June may mature, the seed shatter and 
germinate the same summer. In the 
Illinois River valley this second growth 
of millet has never matured before frost. 
We do not know just how operative the 
above conditions were in lowering the 
value of this species in 1939, but we 
know that the water receded in many 
lake basins 2 weeks earlier in 1940 than 
in 1939 to give the millet a longer grow- 
ing season. 
Giant bur-reed, Sparganium eury- 
carpum, fig. 7, with an index value in 
table 3 of 2.60, ranks as a much better 
duck food plant in the Illinois River val- 
ley than it is generally believed to be. 
Studies by Low & Bellrose (ms.) in 1941 
on the seed yield of this species reveal 
that it produced about three times as 
much seed in areas with stable water 
levels as in areas with semistable water 
levels. In the various types of areas 
combined, giant bur-reed in 1941 pro- 
duced more seed per unit of area than 
either largeseed or nodding smartweed. 
Ducks feed mainly on its 
Coontail, Ceratophyllum demersum, 
fig. 8, ranking slightly below giant bur- 
reed in value, table 3, is an excellent 
Fig. 9.—Duck potato (Sagittarta latifolia) is 
valued by ducks more for its seed than for its 
large, deeply buried tubers. 
