50 



called vermin. All these animals, and crows, also, are to be 

 ranked among the natural enemies of mice. The statement 

 made by Childrey regarding the assemblage of owls when the 

 field mice swarmed in Essex in 1580 received confirmation 

 during 1892. Local observers reported that, after the great 

 increase of voles occurred, the short-eared owl (Asio flammeus) 

 became much more numerous on the hill farms, and that many 

 pairs, contrary to precedent, remained to breed. 



Dr. W. B. Wall expresses the opinion, from his experience 

 with the pests, that their chief enemies are the owl and the 

 kestrel (a hawk), which do more to reduce their ranks than all 

 the traps of the farmers and the "microbes of the scientists" 

 combined. Both farmers and gamekeepers in England and 

 Scotland are inclined to regard these birds as vermin, to be 

 shot at sight. 1 



Any one who doubts that under normal conditions of Nature 

 the natural enemies of field mice can check effectively any 

 irruption of these creatures should read a chapter in one of 

 Hudson's books, entitled "A Wave of Life." He writes of a 

 time when the pampas of the La Plata were mainly a wilderness 

 inhabited only by scattered bands of Indians. He says that 

 in the summers of 1872 and 1873 (which would correspond 

 chronologically with the winter of those years in North America), 

 an unusually fertile and prolific season there, mice became so 

 abundant that domestic fowls pursued them incessantly. Foxes, 

 weasels, cats and even armadillos fared sumptuously. Storks 

 and owls greatly increased in numbers. "On the pampas," he 

 says, "whenever mice, frogs or crickets become excessively 

 abundant we confidently look for the appearance of multitudes 

 of the birds that prey on them." Years may have passed when 

 hardly an individual of any of these birds was to be seen", but 

 now the stork, short-eared owl, black-backed gull, hooded gull 

 and other species appear, a few at first, like harbingers, and 

 before long they arrive in myriads. Short-eared owls remained 

 in numbers, and, supplied with abundant food, began to breed 

 in winter. "As the mice increased," he says, "so did their 

 enemies." Insectivorous and other species acquired the habits 

 of owls and weasels, preying exclusively on mice, while to the 



i Useful Birds and their Protection, 1913, pp. 76-78. 



