1917 BIRDS OF THE SOUTHERN CALIFORNIA ISLANDS 15 
Judging by the data in hand, the whole life cycle of the smaller insular sub- 
species and species, on the more southern islands at least, is shifted a month or 
six weeks earlier than that of the corresponding mainland forms. On San Cle- 
mente Island in 1915, we collected during the last week in March juvenile 
Shrikes, Song Sparrows, Horned Larks, House Finches and San Clemente Wrens 
that were strong on the wing and with well grown tails. These were not isolated 
cases, for after the first day seen, the youngsters at once became common. On 
April 9 I shot a young Song Sparrow that had almost completed the post-juvenal 
molt. On the same date, on San Clemente, however, the larger birds, such as the 
Bald Eagle and the Raven, were not farther advanced in breeding operations 
than one would expect. On Todos Santos Island, April 16, 1910, a pair of Barn 
Owls had a nest containing a chick two-thirds grown, while during the first part 
of the month, on the mainland, I examined two occupied nests which as yet held 
no eggs, though of course Barn Owls sometimes do lay before this date. As pre- 
viously mentioned, there were young House Finches there at the same time that 
were ready to leave the nest, but on the mainland there is not much use looking 
for Linnets’ eggs before the last of March. 
This early nesting may be due to obscure and unrecognized causes, but it is 
partly influenced by the mild winters, and to a greater extent, by the abundant 
food supply. In regard to the latter, it is hard to make comparisons, for on parts 
of the mainland where trees occur, there are large numbers of insects in the tops 
of these, while on an island such as San Clemente they are under one’s feet and 
more readily noticed. Be that as it may, on some of the islands insects are every- 
where, and as there is no frost to reduce their numbers, the birds do not have to 
wait in the spring until the presence of a new generation of bugs enables them to 
begin nesting operations. 
The molt, also, takes place earlier than is usual upon the mainland, and 
birds in fresh plumage may be taken in early August, if not before. March speci- 
mens are sometimes as ragged and faded as mainland ones taken in late June, 
and by the time the new feathers begin to grow some of the birds are almost 
naked. 
Small birds on the islands are particularly numerous, due partly to the 
abundant food supply, in large measure to the absence of many predaceous 
forms, and to the excellent cover afforded by the patches of cactus and thorny 
serub with which the islands abound. Here they usually nest and roost, secure 
from everything except, in the case of the smaller ones, an occasional marauding 
mouse. 
The birds of the Santa Barbara Islands have not lost any of their fear of 
man, as have, for instance, those of the Galapagos Archipelago. The aborigines 
inhabited some of the islands for a long time, and white men have been visiting 
them for many years. On the Coronados I have had Song Sparrows hopping 
about within two feet of my head, but, on the other hand, the Island Shrike is 
the most wary land bird for its size that I have ever encountered. 
The formation of insular races is so shrouded in mystery that it is unsafe to 
speculate as to causes and effects save in a most general way. We can see that 
climate has played an important part in this. As mentioned previously, the gen- 
