VOL. 1.} Distribution of Land Birds. 341 
dent, apparently, of all the islands —is identical with the variety 
characteristic of the coast region of Oregon and Washington.* 
Surely this is a piece of evidence quite out of harmony with the 
theory. To add to the difficulty of accounting for this race, so iso- 
lated from its proper habitat, the Santa Cruz Islands have a warm 
and dry temperature in summer, while the coast district of Oregon 
and Washington is very moist. Such species of powerful flight and 
wide distribution as the fish hawk, prairie falcon, American raven, 
barn swallow and bank swallow, of course, should not be taken into 
consideration in accounting for the distribution of birds, but aside 
from these we find a very considerable percentage of birds to be 
Sonoran in character. Such forms are the rock wren, Bell's finch, 
burrowing owl, California shrike and Baird’s wren, 
This latter bird, which was the only form of Zhkryothorus taken 
on the islands by Mr. Townsend, is a Mexican and Southern United 
States form, which has not been recorded, I believe, from any other 
point on the coast. On the other hand, we find such forms belong- 
ing to the Boreal Province as the western chipping sparrow, spurred 
towhee and lutescent warbler. We see, in fact, that forms charac- 
teristic of both provinces are abundant residents of the islands, and 
we are led to infer that the group belongs to the Transition Region. 
This, of course, implies that the islands are not so completely 
isolated from the mainland, as regards the birds, as they appear to 
be with reference to the plants. Let us see, now, how completely 
isolated the birds are. The nearest islands of the group are not 
over twenty miles from the mainland, and the most distant not over 
a hundred, but with these more distant ones the nearer islands form 
stepping stones to facilitate the passage of transient species. Mr. 
Townsend records from Santa Cruz and Santa Barbara Islands the 
golden-crowned sparrow (Zonotrichia coronata ) in February, which 
species is obviously a migrant there, while the western savannah 
sparrow (Ammodramus sandwichensis alaudinus ), intermediate spar- 
row (Zonotrichia intermedia), and Hutton’s vireo ( Vireo huttont), 
which appear on Mr. Townsend’s winter list, are not recorded by 
Mr. Blake as summer residents, and undoubtedly are not found there 
at that season. Thus it will be seen that the nearest of these islands 
are easily accessible to our sparrows, and presumably to nearly all 
"See Dwight on the Horned Larks, Auk, vii, 2, p. 151- 
