NON-NATIVE GAME BIEBS 41 



the Avorld is temperature ; and this applies fully to game birds. The 

 chief reason why the Gambel Quail of the southeastern deserts did 

 not thrive in central and northern California was that the temperature 

 conditions differed from those to which it had been accustomed in 

 Arizona. The same is true of the Elegant Quail from Mexico. Almost 

 as great a degree of control is to be observed in the case of humidity 

 as in that of temperature. For example, the Ring-necked Pheasant 

 thrives in western Oregon where the relative humidity is greater than 

 in most of California. But the places where these birds have thriven 

 here, namely swamps and tule thickets, afford conditions of high 

 humidity, which compensate for the lack of general atmospheric mois- 

 ture. The same factor was also probably associated with temperature 

 in killing off the Gambel Quail which were introduced into Marin 

 County. Thus climate must be taken seriously into account. 



Finally there are certain factors which are inseparably bound up 

 with the habits of the birds. These pertain to the type of country 

 which the birds inhabit as it relates directly to their modes of life. 

 Grinnell (1914&, p. 96) has pointed out the following three factors in 

 the last named category : 



1. Kind of food supply aflforded, with regard to the inherent structural 

 powers of each of the animals concerned to make it available. 



2. Presence of safe breeding places, adapted to the varying needs of the 

 animals, in other words, depending upon the respective inherent powers of 

 construction, defense and concealment in each species concerned. 



3. Presence of places of temporary refuge for individuals, during day 

 time or night time, or while foraging, when hard pressed by predatory enemies, 

 again correlated with the respective inherent powers of defense and conceal- 

 ment of each species involved. 



An examination of the failures that have attended California's 

 experiments in introduction show that these "associational" factors 

 were probably of much less importance than were temperature and 

 humidity. Possibly the associational elements counted for most in the 

 cases of the Bob-white and turkey. 



Criticism of the trials made in California leads us to two main 

 causes of failure : lack of preliminary investigation of the points just 

 discussed, and improper methods of introducing and liberating the 

 birds. 



In the introduction of foreign species three methods have been 

 used : the immediate liberation of imported adult birds ; the retention 

 of adult birds for a time by responsible parties in aviaries, with sub- 

 sequent liberation of either the adults or young reared by them ; and 

 lastly, the planting of young birds which have been reared in captivity 

 on a game farm. Records show that the first named method, which 

 was that originally employed in Oregon, has given the best results. 



