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 eli- 
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 meau 
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- 
phieally 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 Bay 
Region. 
