150 ANAS STREPERA 
The tracheal dilatation in the male is left-sided and quite similar to that of the 
Widgeon. 
Food. By far the most important study of the food of this duck was made by 
D. C. Mabbott (1920) and other assistants of the U.S. Biological Survey. The 
character of the diet is summarized by his preliminary statement: “The food of both 
the Gadwall and the Baldpate is quite different in some respects from that of the 
Mallard: these two feed to a very large extent upon the leaves and stems of water 
plants, paying less attention to the seeds, while the Mallard feeds indiscriminately 
on both, or even shows some preference for the seeds.” The fact is that the Gad- 
wall is more purely vegetarian, both in summer and in winter, than any of the 
other carefully studied American species of shoal-water ducks. The analysis made 
was based on 417 stomachs, most of which came from birds taken in the autumn 
and winter in Arkansas, Utah, North Carolina, North Dakota, Florida and other 
States. These autumn and winter (September to March) stomachs contained 
over 97% vegetable matter and only about 2% of animal matter. The vegetable 
portion consisted of pond-weeds (42.3%), sedges (19.9%), algse (10.4%), coon-tail 
(7.8%), grasses (7.6%), arrow-heads (3.2%), rice and other cultivated grain (1.3%), 
duck-weeds (0.6%), smart-weeds (0.6%), wild celery and water-weeds (0.5%), 
waterlilies (0.5%), madder family (0.3%), and miscellaneous (2.6%). The predomi- 
nant food is, therefore, the leaves and stems of the pond-weeds. What little animal 
food was taken consisted of a great variety of mollusks, insects (chiefly larval stages) 
and a very few crustaceans. An interesting find was that of reproductive buds of 
fresh-water Bryozoa. 
The summer stomachs of adults, of which there were only thirteen, are especially 
interesting because they contain only 1 1 % of animal food. If this represents a fair 
average, it is certainly a remarkably small amount. The stomachs of eleven young, 
collected mostly in North Dakota, contained water-bugs (56%), beetles (7%), flies 
and their larvae (2%), nymphs of dragon-flies and damsel-flies (0.27%), other in- 
sects (2%), the total animal food being 67.54%. 
A long account of the food of this duck in Europe is given by Naumann (1896- 
1905). There, too, the pond-weed seems to be one of the favorite foods, but ac- 
cording to this writer the Gadwall feeds also on small Conchylia, spawn of fish and 
frogs, and in case of necessity even small fish or frogs. Of the grains, he says, they like 
oats only, though they will feed on rice; but they will not eat barley at any time. 
In India, according to Hume and Marshall (1879), they feed extensively on wild 
or cultivated rice, seeds, leaves and flower-buds of all kinds of rushes and aquatic 
plants, insects and their larvae, and sometimes small worms, but these authors 
never found frogs or fish in Gadwalls’ stomachs. A curious note given by them is 
worth quoting: the Gadwall “may often be seen trotting about on tiny smooth grass 
