WILD DUCKS OF THE BEAR RIVER MARSHES,. UTAH. 17 



the shores of some of the larger overflows. The depreciations of 

 these birds are confined almost entirely to pilfering eggs from the 

 nests, though occasionally they may kill newly hatched ducklings. 

 In a number of places the writer observed ducks' nests that had 

 been broken up by magpies during 1915 and 1916. This was espe- 

 cially the case with nests exposed during haying operations. There 

 is no question that magpies, finding conditions here favorable to 

 their increase, have multiplied to a point where they are directly 

 injurious to other more valuable species. It is a comparatively 

 simple matter to limit their numbers by means of poisoned baits 

 properly used. Under proper conditions one man should be able 

 to reduce them to the desired minimum in two or three weeks' 

 work. 4 It is neither necessary nor profitable to carry poisoning 

 operations far enough to exterminate the birds, but merely to con- 

 trol them to the point of eliminating a large part of the damage. 



Gulls. — Ring-billed and California gulls do not appear to harm the 

 ducks during the breeding season, but during the fall kill a good 

 many that are helpless with the duck sickness. Kavens do a certain 

 amount of damage in the same way, but are not common enough to 

 be considered definitely destructive. The case of the gulls is some- 

 what different, as these birds are abundant and often are present in 

 large flocks. During the shooting season gulls also attack ducks that 

 have been killed by hunters and, not content with eating from one 

 bird, often pick and tear open several, taking only a small portion of 

 flesh from each. From observation it has developed that certain 

 birds may become addicted to this practice, and it is an open ques- 

 tion whether these individuals should be killed to prevent such un- 

 warranted destruction. 



Other birds. — Among bird enemies that have not been mentioned 

 are the duck hawks, which take occasional toll, and the bl^ck- 

 crowned night heron, which at times eats young ducklings. The 

 ducks destroyed by these two are, however, a negligible quantity 

 and do not warrant the persecution of these birds. 



Coyotes. — The coyote is another enemy of the ducks and destroys 

 a considerable number each year. In the delta region of the river 

 these mammals occur during the summer, but do not become common 

 until the middle of August or the first of September, at which time 

 their tracks may be found in abundance. They work through the 

 marshes in search of young ducks and "flappers" and also follow 

 the borders of the bays to secure'birds suffering from the duck sick- 

 ness that has come into prominence here during recent years. 5 Many 



4 Those interested may obtain instructions for preparing properly poisoned baits by 

 writing to the Biological Survey, Washington, D. C. 



B Cf. Wetmore, Alexander, The Duck Sickness in Utah : U. S. Dept. Agr. Bull. 672, 

 pp. 25, pis. 4, 1918. 



