SUPPRESSION OF PESTS BY BIRDS Mr-ATBE. 435 



with birds strictly under control. Poultry are so used against in- 

 vasions of insects, particularly grasshoppers, and native birds have 

 been used in a few instances. Mr. Irving C. Emmett, Federal game 

 warden, reports on the usefulness of — 



the California Valley quail, which was introduced into Utah some few years 

 ago. For a while the farmers objected to this bird, their claim being that it 

 ate considerable of their grain. The alfalfa weevil was first found in the Salt 

 Lake Valley and gradually worked from there northward and west until it 

 covered a great part of the alfalfa district of the western part of the United 

 States. It was noticed, however, that in some localities the weevil affected 

 the alfalfa but very little, while in an adjoining field the entire crop would be 

 taken. Upon investigation it was found that quail were nesting in the fields 

 in which the weevil had not attacked the alfalfa. A number of the most 

 prominent growers then decided to introduce quail into their fields, and they 

 were captured in the fall and put into boxes and partly domesticated during 

 the winter and then taken out into the alfalfa fields and released in the spring. 

 In almost every case these birds remained near where they were released, and 

 nested in the fields or in the brush near to them. In practically every case 

 where these birds were released the alfalfa weevil disappeared. There is one 

 district in particular where this method was introduced, being a stretch of 

 country about 36 miles long between the cities of Ogden and Salt Lake City, 

 and the experiment worked out so well that the farmers in this district will 

 not allow any hunter to kill any quail on his farm, notwithstanding the fact 

 that they are very liberal toward sportsmen and will allow them to hunt on 

 their lands for other birds, but look upon the quail as one of their greatest 

 friends. 



Another instance involving the introduction of birds is reported 

 by Dr. Samuel G. Dixon, late health commissioner of Pennsylvania. 

 He writes : 45 



After trying the ability of fish to devour larvae and pupae of mosquitoes 

 with varied success, I built two dams near together on the same stream, so 

 that each would have the same environment for the breeding of mosquitoes. 

 Each covered nearly 1,400 square feet. In one 20 mallard ducks, Anas platy- 

 rhijncha, were permitted to feed, while the other was entirely protected from 

 waterfowl, but well stocked with goldfish Carassius auratus, variety americanus. 



The one in which the ducks fed was for several months entirely free from 

 mosquitoes, while the pond protected from ducks and stocked with fish was 

 swarming with young insects in different cycles of life. 



To the infested pond 10 well-fed mallard ducks, Anas platyrhyncTia, were 

 then admitted, and as they entered the pond they were first attracted by the 

 larval batrachians, tadpoles. They, however, soon recognized the presence of 

 larvae and pupae of the mosquito and immediately turned their attention to 

 these, ravenously devouring them in preference to any other foodstuffs present. 

 At the end of 24 hours no pupae were to be found and in 48 hours only a few 

 small larvae survived. The motion of the water made by the ducks, of course, 

 drowned some of the insects — what proportion can not be estimated. 



For some years I have been using clucks to keep down mosquitoes in swamps 

 that would have been very expensive to drain, but I never fully appreciated 

 the high degree of efficiency of the duck as a destroyer of mosquito life until 

 the foregoing test was made. 



45 Journ. Amer. Med. Assn., vol. 63, No. 14, p. 1203, Oct. 3, 1914. 



