FOOD HABITS OF SHOAL-WATER DUCKS. 7 
stomachs examined were collected in the swamps of Louisiana, 
Arkansas, and other localities where duckweeds abound, but the 
majority failed to disclose any duckweeds. Only 17 of the total 
number of ducks had eaten duckweeds (Lemna spp.), and some of 
these only in very limited quantities. 
SMARTWEEDS (POLYGONACEAE), 0.59 PER CENT. 
_ The Polygonaceae is one of the families of plants of which the seeds 
alone furnish an important article of food for birds. Thisvery probably 
is the reason why smartweeds are only one of the minor items in the 
food of the gadwall. The following species were identified from the 
stomachs examined: Dock-leaved smartweed (Polygonum lapathi- 
folium), found in 5 stomachs; water smartweed (P. amphibiwum), 
in 3; and knotweed (P. aviculare), Pennsylvania smartweed (P. 
pennsylvanicum), water pepper (P. hydropiper), lady’s-thumb (P. 
persicaria), mild water pepper (WP. hydropiperoides), and prickly 
smartweed (P. sagittatum), in 2 each. Seeds of black bindweed 
(Polygonum convolvulus) and another species (P. opelousanum) were 
present in 1 each, unidentified smartweeds in 2, and seeds of dock 
(Rumex spp.) in 2. Smartweed seeds were present usually in small 
numbers, but the gullet of one bird taken in Montana was crammed 
with sant 3,000 seeds of water pepper, in addition to a few of dock- 
leaved amnantanee 
FROGBIT FAMILY (HYDROCHARITACEAE), 0.53 PER CENT. 
Wild celery (Vallisneria spiralis) was found in the stomachs of 3 
birds shot on Mobile Bay, Alabama, and waterweed (Philotria spp.) 
had been eaten in generous quantity by a bird from southern 
Wisconsin. Wild celery is a very important food item of some 
species of ducks. | 
WATERLILY FAMILY (NYMPHAEACEAE), 0.52 PER CENT. 
Two gadwall stomachs collected in Florida were filled with the 
seeds of. a white waterlily (Castalia sp.), one containing about 1,100 
and the other 1,200 seeds. Another from the same State contained 
28 of the hard ovoid seeds of water shield (Brasenia schrebert). 
MADDER FAMILY (RUBIACEAE), 0.37 PER CENT. 
Twenty-three gadwalls had eaten seeds of buttonbush (Cepha- 
lanthus occidentalis). These seeds are narrowly wedge shape and are 
borne like miniature sycamore balls in spherical clusters on the ends 
of the branches of the plant, which is a shrub or small tree growing 
in wet places. They had been eaten by few of the ducks in any 
great numbers, but in some instances they constituted the greater 
part of the stomach contents. 
