NON-NATIVE GAME BIBDS 43 



As an example under the second point, it is well known that the 

 English Sparrow and our native Linnet do not get along well together. 

 The former is aggressively pugnacious in disposition, and drives the 

 Linnet off the premises by individual combat. In any case it is certain 

 that, since at the season of minimum food supply, about February and 

 March, the struggle for existence is very keen, both because of food 

 shortage and because of persecution by carnivorous enemies, and since 

 the number of birds that can persist through this critical season 

 depends absolutely upon the amount of sustenance then available, the 

 introduction of foreign birds will inevitably bring injury to the native 

 species. Some peculiar advantage in food-getting power on the part 

 of the introduced birds may increase this peril still further. 



Finally, there is the question of disease. Parasites and disease 

 organisms are very likely to be brought in by exotic birds, and the 

 conditions may prove favorable to their spread among our native game 

 species. Because of the abruptness of the exposure, our birds will 

 not have acquired immunity from those parasites and diseases, and 

 wholesale mortality is likely to result. It is undesirable that the exist- 

 ence of our native birds should be jeopardized in this manner for the 

 mere chance of a successful introduction of any sort of foreign game. 

 In 1916 quail from Mexico were prohibited entry into the United 

 States because of the prevalence of a "quail disease" in their native 

 country. 



Summary 



A review of the attempts to acclimatize foreign game birds in 

 California shows that the success attained has not been commensurate 

 with the money and energy expended, and that two of the underlying 

 causes of failure have been the lack of careful preliminary investiga- 

 tion of the factors controlling acclimatization, and the improper 

 method of liberation. Every introduced species must meet certain 

 requirements, the chief of which relate to the climatic conditions of 

 temperature and humidity, the food supply, the safety of breeding 

 places, and the availability of suitable cover for protection from 

 enemies. Not one, but many, limiting conditions must be satisfied; 

 hence the chances that a given species will succeed in a new environ- 

 ment are small, and, also, the number of species possessing the neces- 

 sary all-around adaptive ability is small. The possibility of establish- 

 ing a foreign game species has been demonstrated in the case of the 

 pheasant in Oregon, and more carefully planned undertakings here 

 might lead to success in the case of other game species. Even though 

 a foreign species proves to be desirable, there is always the attendant 

 danger that the introduced bird will wholly supplant some native one, 



