FOOD HABITS OF SHOAL- WATER DUCKS. 33 



hristylis and Carex also were taken very frequently by these ducks. 

 As many as 1,500 seeds of beaked rush, 3,000 of the three-square, 

 3,600 of spike rush, and 9,000 of Scirpus cubensis were counted from 

 various single stomachs, while one' contained more than 150 of the 

 large, horned seeds of beaked rush (Rhynchospora corniculata) . 



GRASSES (gRAMINEAe), 9.64 PER CENT. 



Grass remains in the pintail's food consist also very largely of seeds. 

 Many of the stomachs contained the seeds of switchgrass (Panicum 

 sp.), barnyard grass or wild millet (EchinocMoa crus-galli), wild rice 

 (Zizania palustris), cut grass (Zizaniopsis miliacea), salt grass (Dis- 

 tichlis spicata), and foxtail (Chaetochloa sp.), often in very large num- 

 bers. One was found to contain 11,500 seeds of barnyard grass, 

 and another held nearly 4,000 of switchgrass. Included in the grass 

 family are cultivated rice (Oryza sativa) and other grains. Rice was 

 found in 52 of the pintail stomachs — 24 of them from Texas, 18 from 

 Louisiana, and 10 from Florida. Many were crammed with rice 

 kernels, and contained nothing else, but all were taken during the 

 months of November, December, and February, so there can be no 

 doubt that it was all waste grain. Of the other cultivated grains, 

 corn was found in 3 stomachs, wheat in 3, barley in 3, and oats in 1. 

 This also probably was waste grain, with the exception of oats, 

 taken in North Dakota in June, and a few grains of wheat taken in 

 Colorado in March. 



SMARTWEEDS AND DOCKS (pOXYGONACEAe), 4.74 PER CENT. 



Many of the plants of the family Polygonaceae grow in or near 

 water and their seeds are eaten by a great many different kinds of 

 birds. The seeds of mild water pepper (Polygonum liydropiperoides) , 

 found in 29 stomachs, and of water smartweed (P. amphibium), in 23, 

 seem to be the favorites with the pintail. Several also had taken 

 seeds of prickly smartweed (P. sagittatum) , kno tweed (P. aviculare), 

 Pennsylvania smartweed (P. pennsylvanicum) , water pepper (P. 

 Jiydropiper) , and other smartweeds (P. lapatMfolium, P. persicaria, 

 and P. opelousanum) . About 12,500 seeds of a smartweed, Poly- 

 gonum punctatum, were found in the crammed gullet and gizzard 

 of one pintail from Alabama. Seeds of dock (Rumex sp.) were 

 present in 7 gizzards. 



arrow-grass (Triglochin maritima) , 4.52 per cent. 



Arrow-grass is a plant of the marshes, muddy shores, or low 

 meadows near salt water. The seeds are borne on erect spikes, and 

 are the only parts of the plants commonly eaten by the birds. Eighty- 

 eight pintail stomachs, all from the Pacific coast of Washington, 

 179375°— 20 3 



