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. This very 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 smaftweed (Polygonum lapaihi- 

 folium), found in 5 stomachs; water smartweed (P. ampMbium), 

 in 3; and kno tweed (P. aviculare), Pennsylvania smartweed (P. 

 pennsylvanicum) , water pepper (P. hydropiper) , lady's- thumb (P. 

 persicaria), mild water pepper (P. Jiydropiperoides) , 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 about 3,000 seeds of Water pepper, in addition to a few of dock- 

 leaved smartweed. 



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 schreberi). 



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. 



