FOOD HABITS OF SHOAL- WATER DUCKS. 25 



SMARTWEEDS (pOLYGONACEAe), 8.22 PER CENT. 



Two of the blue-winged teals had eaten seeds of dock (Rumex sp.). 

 All other seeds of this family taken were of the true smartweeds 

 (Polygonum spp.). These were represented by 9 species, and 16 

 stomachs contained unidentified smartweed seeds. Mild water 

 pepper (Polygonum Jiydropiperoides) , which was found in 31 stomachs; 

 water smartweed (P. ampMbium), in 27; and dock-leaved smartweed 

 (P. lapathifolium) , in 26, were the kinds most often found. Other 

 species taken were prickly smartweed (P. sagittatum), lady's-thumb 

 (P. persicaria), water pepper (P. Jiydropiper) , Opelousas smartweed 

 (P. opelousanum) , Pennsylvania smartweed (P. pennsylvanicum) , and 

 dense-flowered smartweed (P. portoricense) . 



ALGAE, 2.95 PER CENT. 



The greater part of the seaweeds taken consisted of musk grass 

 (Cham spp.). Several stomachs collected in Wisconsin, North Da- 

 kota, and Florida were nearly full of this alga, chiefly the oogonia, 

 or reproductive cells. Altogether, musk grass was found in. 31 

 stomachs, and unidentified marine algae, or seaweeds, in 4. 



WATERUXIES (NYMPHAEACEAE), 1.37 PER CENT. 



Waterlily seeds had been taken by 27 of these teals. Fourteen had 

 eaten seeds of white waterlilies (Castalia -sp.), and the other 13 had 

 eaten those of the small purple waterlily known as water shield 

 (Brasenia schreberi). Most of the white waterlily seeds were found 

 in the stomachs of a series of ducks collected in Florida. One of 

 these, together with the bird's gullet, which was also full, contained 

 1,600 seeds and fragments of many more. 



WATER MILFOILS (HALORAGIDACEAE), 0.71 PER CENT. 



The plants of the family Haloragidaceae have a very wide geo- 

 graphic distribution. They are chiefly aquatic, and have hard, 

 nutlike seeds which persist for some time in bird stomachs. The 

 three North American genera were represented in the stomachs 

 examined, bottle brush (Hippuris vulgaris) in 8, mermaid weed 

 (Proserpinaca sp.) in 5, and water milfoil (Myriophyllum sp.) in 44. 



BUR REEDS (SPARGANIACEAE), 0.38 PER CENT. 



The seeds of bur reed (Sparganium sp.) had been eaten by 39 of 

 the blue-winged teals examined, but usually were found in small 

 numbers. 



MADDER FAMILY (RUBIACEAE), 0.35 PER CENT. 



The madder family was rather sparingly represented by seeds of 

 buttonbush (Cephalanthus occidentalis) , found in 5 stomachs; bed- 

 straw, or cleavers (Galium sp.), in 10; and rough buttonweed (Diodia 

 teres) in 1. 



