FOOD HABITS OF SHOAL- WATER DUCKS. 11 



pate appears to be even less of a seed eater than the gadwall. 

 Sedges (Cyperaceae), consisting almost entirely of seeds, amounted 

 to 19.91 per cent of the food of the gadwall, but to only 7.41 per cent 

 of the food of the baldpate. The baldpate also ate more wild celery 

 (Vallisneria spiralis), grasses, and water milfoils (Hippuris vulgaris 

 and Myriopliyllum sp.), but much less coontail (CeratopJiyllum. 

 demersum) . 



Investigation of the food habits of the baldpate consisted chiefly 

 of an examination of the contents of 255 stomachs, 5 collected (all but 

 4) during the months from September to April, inclusive, from 25~ 

 States, 4 Canadian Provinces, Alaska, and Mexico. With the excep- 

 tion of series of 53 from Utah, 50 from Oregon, and 29 from North 

 Carolina, they were very evenly distributed in numbers among the 

 different States and Provinces. Four stomachs of birds shot in May 

 and June, together with 22 others which were too nearly empty to 

 allow accurate estimates of percentages of food contents, were not 

 included in the computation, so that the results given are from the 

 remaining 229 stomachs. In the list of food items, however, material 

 from all stomachs is included. 



Vegetable Food. 



The vegetable food of the baldpate for the 8 months from September 

 to April averaged 93.23 per cent. This consisted of the following 

 items in the order of their importance: Pondweeds, 42.82 per cent; 

 grasses, 13.9; algae, 7.71; sedges, 7.41; wild celery and waterweed, 

 5.75; water milfoils, 3.48; duckweeds, 2.2; smartweeds, 1.47; arrow- 

 grass, 0.36; waterlilies, 0.26; coontail, 0.24; and miscellaneous, 7.63 

 per cent. 



PONDWEEDS (NAIADACEAE), 42.82 PER CENT. 



Pondweeds are by far the most important item of food of the bald- 

 pate, as well as of the gadwall and several other species of ducks. 

 Of the 229 baldpate stomachs, 157, or more than two-thirds, con- 

 tained pondweeds in some form or other. True pondweeds (Pota- 

 mogeton spp.) were found in 102 stomachs, widgeon grass (Ruppia 

 maritima) in 92,- eelgrass (Zostera iiMrina) in 10, bushy pondweed 

 (Najas jiexilis) in 9, and horned pondweed (Zannicliellia palustris) 

 in 8. As in the case of the gadwall, the parts of the pondweeds eaten 

 by the baldpate were almost exclusively leaves and stems, with com- 

 paratively few seeds, and birds taken from several different localities 

 evidently had been feeding upon pondweed foliage almost exclusively. 

 One of the plants of this family {Ruppia maritima) seems to be well 

 entitled to its common name "widgeon grass," as its foliage is fed 

 upon by the widgeon even more extensively than by the gadwall. 



5 Sixty-four of these were examined by W. L. McAtee. 



