io6 
THE CONDOR 
| Vol. VII 
been visited once only by an ornithologist since 1867," that once being by Mr. C. 
H. Townsend in 1889/ at which time a limited period only was spent on the 
islands and the meagre knowledge ol the avifauna that was obtained, important as 
it was, served only to whet the interest of all western ornithologists. Since 1897 
several expeditions have touched at these islands en route to and from the Galap- 
agos group, and one expedition was sent to Los Revillagigedos by the California 
Academy of Sciences in 1903. This party spent several months in the region, 
principally upon Socorro Island, and the report of their work, when published, 
will undoubtedly add much to the history of the group. 
Most of the islands along the coast-line of Lower California were at one time 
an integral part of the mainland. San Martin Island, however, is undoubtedly of 
volcanic origin and of comparatively recent eruption, the lava blocks being sharp 
and clean-cut on the edges. Guadalupe also is of volcanic origin but is older than 
San Martin, the lava on Guadalupe being well weather-worn. Cerros Island, 
while at one time part of the mainland, shows traces of volcanic disruption in the 
torsion of the strata, but no direct eruptive evidences were seen. Socorro and San 
Benedicte Islands, however, are strikingly volcanic, the former being in reality an 
active volcano, while San Benedicte is a vast heap of broken lava, pumice, tufa, 
ashes and obsidian. San Benedicte has but little vegetation, that little being main- 
ly grasses, but on Socorro soil has formed and the island is a dense growth of cac- 
tus, grasses, vines, shrubs and even large trees; this, taken together with the ex- 
tensive and peculiar avifauna, shows the great age of Socorro as compared with San 
Benedicte. Clarion Island, also, owes its origin to volcanic sources and to the sub- 
sequent action of the corals which have surrounded the island with reefs. The 
vegetation on Clarion is dense and consists principally of cactus; on some portions 
of the island a tree ( Dodoncza viscosa L.) is abundant, and it is on the tops of these 
trees that the boobies (Sid a piscatriA webstcri ) nest by thousands. These trees are 
undergrown by and interlaced with a network of thorny creepers (Ccrsalpinia bon- 
ducella Roxb.), peculiarly tough and clinging, and these creepers aid the cactus in 
making locomotion impossible without the aid of a machete to cut a path. These 
thorn creepers are also a source of great danger to the boobies nesting over them, 
for if a booby misses alighting on the nest when returning heavy laden with fish, 
or if in rising the heavy bird falters and drops, the thorny ropes seize him in a 
grasp that never relaxes; to this we found many a skeleton bearing grim testimony. 
The writer regrets exceedingly that lack of time and space prevent his giving 
to this list the detail it warrants. Much might be written on the curious habits of 
these little-known species, especially on the breeding habits, many nests and eggs 
having been found, and of species whose nesting habits were and are unknown to 
the majority of workers. 
Colymbus nigricollis californicus (Hef.rm.). We saw one individual of this 
species on San Geronimo Island on March 17th; it is reported commonly from the 
coast of Lower California in winter. 
Cerorhincha monocerata (Pale.). Rhinoceros Auklet. A single specimen was 
taken near San Geronimo Island about March 9th, 1899. 
Ptychoramphus aleuticus (Pall.). Cassin Auklet. This species is common 
on all the islands as far south as Ascuncion Island, becoming abundant on San 
Geronimo, San Benitos and Natividad Islands, less common on Todos Santos, San 
Martin, San Roque, Ascuncion and Cerros Islands; this is probably the most abund- 
a. Cf. Grayson, Col. A. J ., Exploring Expedition to the Island of Socorro. I’roc. Bost. Soc. Nat. Hist., XIV, 1870-71, 
287-289. 
b. Cf. Townsend, C. H., Birds from the Coast of Western North America and Islands, etc. Proc. U. S. Nat. Mus. 
XIII, 1S90, 131-142. 
