1918] Swarth: The Pacific Coast Jays of the Genus Aphelocoma 419 
The Santa Cruz jay is one of the most sharply differentiated of 
any of the island species, and it is hard to appreciate the possibility 
of the development of the form under the given conditions. Santa 
Cruz is the only one of the Santa Barbara Islands upon which jays 
of any sort are found, though other species of birds far more sedentary 
in their manner of life, are widely distributed over the group, and 
conditions upon some, at least, of the other islands would permit the 
existence of the jay. Santa Cruz is not so widely distant from the 
mainland but what it would seem possible for jays to travel back and 
forth. While the California jay of the adjacent mainland strictly 
speaking is not a migratory species, still in the fall small flocks may 
oceasionally be seen wandering far from their breeding grounds, in 
territory where they certainly never nest, and it would seem not 
unlikely, under the circumstances, for individuals from the mainland 
to reach the islands occasionally, and vice versa. 
Then, as regards the extreme differentiation achieved by the 
Santa Cruz jay, it is of interest to make comparisons with other 
variable forms occurring upon the same island. 
The spotted towhee (Pipilo maculatus) as it occurs upon Santa 
Cruz is indistinguishable from the mainland subspecies, megalonyx, 
though upon others of the islands there is the subspecies clementae, 
with strongly developed characters. The Bewick wren (Thryomanes 
bewicki) upon Santa Cruz Island is recognized separately, as the 
subspecies nesophilus, but it is with difficulty distinguished from the 
race charienturus upon the adjoming mainland, while again upon 
other of the islands there are races with much more strongly marked 
features. The bush-tit (Psaltriparus minimus), Hutton vireo (Vireo 
huttont), and perhaps one or two other species, occur upon Santa 
Cruz alone of the Santa Barbara Islands—as does the jay—yet none 
of these have developed into recognized insular races. 
On the whole it is evident that Santa Cruz Island has not served 
as a differentiating center to the same extent as other islands of the 
group; yet at the same time it has produced in the Santa Cruz jay 
the most strongly characterized of any of the island races. 
The most striking feature of the Santa Cruz jay, as compared with 
the mainland species is its enormous size, so in this case a marked 
restriction of range, with consequent probability of inbreeding of 
closely related individuals has not been productive of the dwarfed 
stature which such conditions are supposed to engender. 
