TOOD HABITS OF SHOAL- WATER DUCKS. 15 



reed (Sparganium sp.), myrtle (Myrica sp.), saltbush (Atriplex sp.), 

 purslane (Portulaca sp.), crowfoots (Ranunculus spp.), brambles 

 (Rubus spp.), clovers (Melilotus sp. and Medicago denticulata) , spurge 

 (Croton sp.), sumac (Rhus sp.), holly (Ilex sp.), water hemlock 

 (Cicuta sp.), and many others. 



Animal Food. 



Animal food amounted to 6.77 per cent of the contents of the 229 

 baldpate stomachs included in the computation. Even this figure is 

 probably unduly large, because the greater part of the animal matter 

 consisted of snails found in the gizzards of a series of ducks from 

 southern Oregon, the only lot of birds found feeding almost exclu- 

 sively upon such food. More than nine-tenths of the animal food 

 (6.25 per cent of the total) consisted of mollusks, the remainder 

 being made up of insects (0.42 per cent) and miscellaneous matter 

 (0.1 per cent). 



MOLLUSKS (MOLLUSCA), 6.25 PER CENT. 



Fragments of small bivalves were found in 6 stomachs, and snails 

 (univalves) in 29. As already stated, the greater part of the mol- 

 lusks were from a number of Oregon ducks, taken along the shores of 

 the Klamath River. Many of them had gorged themselves upon 

 snails, and these constituted practically 100 per cent of the contents 

 of 13 out of the 17 stomachs in the series, of which 7 contained nothing 

 else. Two other baldpates, one from Lake Michigan near Chicago, 

 and the other from Lake Manitoba, Canada, had fed largely upon 

 mollusks. 



INSECTS (iNSECTA), 0.42 PER CENT. 



Insects which amounted to only 0.42 per cent of the food of bald- 

 pates included in .our investigation probably are eaten to a greater 

 extent during the summer months, especially by the ducklings. No 

 ducklings of this species were available, but there can be little doubt 

 that, like the young of the gadwall, they feed largely upon the adults 

 and larvae of aquatic insects. 



More than two-thirds of the insects eaten by the baldpate (0.29 

 per cent of the whole) were beetles. These included water scavenger 

 beetles (Hydrophilidae), found in 8 stomachs; predacious diving 

 beetles (Dytiscidae), in 2; leaf chafers (Scarabaeidae), in 2; leaf 

 beetles (Chrysomelidae), in 3; weevils (Rhynchophora) , in 2; Derme- 

 stidae, in 2 ; and unidentified fragments of beetles, in 16. One gizzard 

 contained about 85 individuals of a species of rove beetle (Staphylin- 

 idae), a small, elongated, soft-bodied insect, which is usually very 

 common about decaying animal matter. 



Flies and their larvae arid pupae furnished 0.09 per cent of the food. 

 Twelve baldpates had eaten midges (Chironomidae) ; 9, ephydrid 

 flies (Ephydridae) ; 3, craneflies (Tipulidae); 1, flies of the family 



