WILD DtTCKS OF THE BEAR RIVER MARSHES, UTAH. 15 



importance to merit attention. Any of the clucks will turn to animal 

 matter for sustenance when it is readily available and snap up in- 

 sects or even small minnows that may be accessible, though normally 

 the bulk of their food may be vegetable matter. There are, however, 

 at the mouth of Bear Kiver, a few species belonging to the animal 

 kingdom present in such numbers as to form a food supply upon 

 which some ducks feed to large extent during part of the year. Be- 

 low the lower end of the marsh, where saline conditions are so pro- 

 nounced as to prevent vegetable growth, are great quantities of the 

 immature stages of several species of alkali flies (Ephydra hians, 

 E. siibopaca, and E. gracilis). The larvse and pupse of these insects 

 form great masses in the water and the cast-off pupal cases are 

 washed up in windrows that frequently extend, for miles along the 

 shores of the lake. With them in equal numbers, or possibly ex- 

 ceeding them in abundance, are the fairy or brine shrimps (Artemia 

 fertilis). These small, almost transparent creatures are so abundant 

 that they form veritable clouds in the water, and these, with the fly 

 larvse and pupae, form an important source of food for certain 

 species of ducks and also for various shorebirds. 3 After the summer 

 molt spoonbills, or shovelers, begin to gather in the lower bays, and 

 by September 1 are present in considerable numbers. The flocks 

 continue to increase, until by October 1 it is not unusual to see close 

 banks of these birds 2 miles or more long and from a fourth to half 

 a mile deep. At this time the birds feed largely on the brine shrimps 

 and on alkali-fly larvae and pupse. They remain here until finally 

 driven out by the freezing of the fresh-water bays, to which they 

 resort to drink. Usually the shoveler is thin and poor in body, but 

 birds killed here were exceedingly fat, so that while this species 

 ordinarily is considered a mediocre table bird, those killed on the 

 lower bays were good eating. 



During October the spoonbills were joined by great flocks of 

 lesser scaup ducks {Mania affinis) and later by a considerable num- 

 ber of golden-eyes, or whistlers (Clangula clangula americanq), and 

 all subsisted largely upon the brine shrimps and the immature 

 alkali flies. These ducks were found regularly only in this part of 

 the bay and it was unusual to see them higher up. Ducks shot in 

 this lower area often were crammed with food, so that when the 

 birds were picked up by the feet brine shrimps and fly larvse oozed 

 in a slimy mass from their throats. It is hardly necessary to point 

 out the value of these supplies of animal food as an additional at- 

 traction to bring wild ducks to this marsh. 



3 Cf. Wetmore, A., On the Fauna of Great Salt Lake : Amer. Naturalist, vol. 51, pp. 

 753-755, 1917. 



