52 AN ECONOMIC STUDY OF FIELD MICE. 



husking time as they hover in the air or sit on a fence post or top of 

 a hedge, ready to pounce upon every mouse that escapes from corn 

 shocks as they are torn down or moved. 



The smaller shrikes (Lanius ludovicianus and subspecies) also 

 somewhat resemble mocking birds in color. They are summer resi- 

 dents of many parts of the United States. As insects are abundant 

 during the greater part of their stay, they are insectivorous to a 

 greater extent than the northern shrike. Stomach examinations 

 prove that mice form If) per cent of the food for the entire year, but 

 the birds are less able than the larger species to cope successfully 

 with adult meadow mice, yet they undoubtedly destroy a good many 

 voles, and several have been identified in their food; but smaller 

 mice are more frequently caught. - 



Although shrikes destroy a few useful birds, they more than com- 

 pensate for this by their destruction of small rodents and insects, and 

 they fully merit protection by the farmer. 



OTHER BIRDS. 



Members of the order Ilerodiones, including herons, storks, and 

 ibises, are usually persistent enemies of meadow mice. Many of 

 them frequent meadows and swamps, especially in the breeding sea- 

 son. Unfortunately, the summer range of the larger number of spe- 

 cies is too far south to bring them much in contact with voles. How- 

 ever, a few species spend the summer where mice abound and make 

 them an important part of their food. 



Of our herons, the American bittern (Botaurus lentiginosus) is 

 probably the best known destroyer of voles. The bird is a summer 

 resident in all suitable localities in temperate Xorth America, making 

 its home in moist meadows, bogs, and swamps. Baird, Brewer, and 

 Ridgway say of it : " It does not move about much by day, although 

 it is not strictlv nocturnal, but is sometimes seen flying low over the 

 marshes in pursuit of short-tailed or meadow mice, which are fre- 

 quently taken whole from its stomach.' 1 a Records of the Biological 

 Survey contain a number of instances in which meadow mice were 

 found in stomachs of this species. 



Among other Herodiones that feed upon meadow mice are the least 

 bittern (Ardetta eosilis), wood ibis (Tantalus locidator), great blue 

 heron (Ardea herodias), American egret (Herod ias egretta), snowy 

 heron (Egretta candidissima) , and the black-crowned night heron 

 (Nycticorax nycticorax ncevius). T\ nile frogs, fish, and fresh-water 

 crustaceans form the major portion of their food, they feed also upon 

 mice, shrews, and other small mammals. As a group they undoubt- 

 edly eifect a reduction in the numbers of meadow mice in America. 



During a plague of field mice (Peromyseus in this case) in South 

 America in 1872-73 Mr. AY. H. Hudson observed that storks became 



a The Water Birds of North America, vol. 1, p. 70, 1884. 



