118 



THE AMERICAN NATURALIST 



[Vol. LI 



locality. The frontier individuals, those on the margin of the 

 habitat of the species, may not prosper as greatly, or reproduce 

 as prolifically, as those in the metropolis of their species ; but they 

 certainly do not, as a rule, beat themselves to death individually 

 against their limiting barrier, of whatever nature it may be. 



To resume the main topic of this discussion, I shall attempt to 

 show that it is possible from field observation to indicate in the 

 case of certain species, some, at least, of the factors which con- 

 trol their distribution ; and further that we who live in Califor- 

 nia have splendid opportunities to gather and examine data by 

 means of which the general laws of animal distribution can be 

 determined. An area within comparatively easy reach presents 

 a wide diversity in topographic and climatic features. Occupy- 

 ing this area is an abundant complement of the higher vertebrate 

 classes. "Within the political limits of the state, systematists now 

 recognize the presence of 388 species of mammals, 543 of birds, 

 79 of reptiles and 37 of amphibians. We have plenty of ma- 

 terial to work with. I shall proceed to discuss a few selected 

 species about which we seem to have knowledge enough to war- 

 rant provisional inferences. 



The Case of the Oregon Jay 



The Oregon jay (Perisoreus obscurus), a close relative of the 

 Canada jay, or whisky-jack, occurs in California only in the 

 northern third of the state. Even there it is very local in its oc- 

 currence and absolutely non-migratory. On the Warner Moun- 

 tains, Modoc County, it ranges from the highest parts down to 

 7,000 feet altitude. On Mount Shasta it ranges from near tim- 

 berline down to about 6,000 feet altitude. It is absent for a 

 long distance to the west, through the Trinity mountain mass, 

 but it recurs along the seacoast of Humboldt County, within fifteen 

 miles of the ocean. And here is the curious point: along this 

 coast strip it does not range higher than 300 or 400 feet above 

 sea level, although there are mountains not far inland which rise 

 to an altitude of several thousand feet. Let us look into this 

 case for the purpose of determining the factors responsible for 

 this interrupted range. 



The Oregon jay, like most members of the crow family, is not 

 restricted in diet. It eats a great variety of both vegetable and 

 animal substances; its food varies in character according to 

 season and local conditions. The supply of any particular kind 



