1917 13 



PROBLEMS PRESENTED BY THE ISLAND AVIFAUNA 



The climate of the islands, taken as a whole, is more equable and humid than 

 that of the mainland coastal plain nearby. Although rainfall records are lack- 

 ing, it is common belief that even the islands nearest shore receive slightly less 

 rain than does the adjacent mainland. This is to be expected, for the nearer one 

 approaches to the mountains, the heavier is the annual rainfall. Those islands 

 farthest from the coast have a still smaller precipitation, and are corresponding- 

 ly more barren. The increased humidity, despite the lesser rainfall, is caused by 

 the modifying influences of the surrounding sea and frequent fogs. The cli- 

 mate of any one of the larger islands shows much variation, according to expos- 

 ure. The seaward sides are subjected to dense fogs and heavy winds, tending to 

 raise the average temperature in winter and lower it in summer. The compara- 

 tively sheltered landward sides are much warmer during the summer months, 

 occasionally presenting an aspect that is decidedly Lower Sonoran, though in 

 reality, the Upper Sonoran is the lowest, and by far the most prevalent zone that 

 occurs. In winter the temperature is higher than it is at the same altitude on the 

 nearby mainland coast, due again to the sea ; frosts are unknown, except possibly 

 on the higher parts of the islands. 



On some islands there are high, grassy ridges and tablelands, in strong con- 

 trast to the wooded canyons, and on Santa Cruz, pine forests, which, while prob- 

 ably of a Transition nature, present features decidedly boreal in appearance. 

 Although certain characteristics of other parts of this and other islands impress 

 one as being in a higher zone than Upper Sonoran, I am of the opinion that these 

 pine forests are the only spots in the region that will bear out such an impres- 

 sion. Taken as a whole, the climate of the islands probably has a lower mean 

 temperature than that of the adjacent coastal plain, which would tend to give 

 them a climate somewhat approaching that of the coast farther north, though not 

 with any conspicuous effect upon the flora and fauna. 



The Santa Barbara Island Faunal Area, as a division, would seem to be con- 

 sidered such more because of convenience and its geographical position, than be- 

 cause of any general uniformity or peculiarity of animal or plant life. Geogra- 

 phically it is segregated from the rest of the state, and the distinct insular forms 

 afford an apparent reason for terming it a separate faunal area ; in reality it is 

 made up of an infusion from several of the other California divisions. In the 

 main, it is clearly San Diegan, but it also contains elements of the Sierran Area, 

 and to a greater extent is suggestive of the more humid northern coast district, 

 not so much of the Humid Coast Faunal Area as, say, of the San Francisco Baj'- 

 Region. 



