150 BULLETIN 107, UNITED STATES NATIONAL MUSEUM, 
of caves are also used, and I have even found them in slight hollows made by 
the birds themselves beneath dense bushes on the hillsides, but I have never 
known a bird of this species to occupy a burrow in soft ground. One egg is 
nearly as often found as two, but this is frequently addled, and I believe that 
the larger number constitutes the normal set. Nests are located from a couple 
of feet above high-water mark to the very tops of the islands. No material is 
used in construction, and a surprising number of eggs are cracked by the sharp 
rocks with which they come in contact. 
Mr. Henry B. Kaeding (1905) reports this species as— 
fairly common on and about Todos Santos, San Martin, San Geronimo, and San 
Benitos Islands, breeding most accessibly on San Benitos, where, in addition to 
nesting in the crannies in the cliffs, the nest is often placed under the foliage 
of the maguey (Agave shawi), on the sandy slopes facing the sea. The eggs, 
taken March 27, were slightly incubated. 
Xantus’s murrelet is credited with raising two broods in a season. 
Mr. Howell (1910) says: 
From my observations, it seems to be beyond doubt that these birds nest 
twice during the year, once toward the last of March, as has been proved time 
and again, and once more during the middle of June; for I found fully as 
many of their eggs at this latter date as did Mr. P. I. Osburn earlier in the 
season. Mr. Osburn has done considerable collecting here within the last few 
years, and spent four days with me during June. I have even taken half- 
incubated eggs from under the sitting bird as late as July 11, and it seems 
hardly likely that one nesting could straggle along continuously from March 
until July. And besides, no ornithologist has ever taken eggs of this species 
in May, as far as I can find out, and there are plenty of them who have 
visited the islands in that month in order to collect eggs of the other kinds of 
birds that are found nesting here. 
H#ggs.—Kither one or two eggs constitutes a full set. In sets of 
two the eggs are often very different in color, suggesting the possi- 
bility that they may have been laid by two birds. Often one of the 
two eggs is infertile. Mr. Howell says that 48 hours elapse between 
the laying of the two eggs. The eggs are subject to great variations 
in color and markings. Mr. Howell has handled a large series of 
these eggs and writes to me that— 
None of our sea birds except the murre exhibits as much variation in their 
eges as does hypoleucus. Those even of the same set run from an almost 
solid dark chocolate to a plain sky blue with a very few spots, but the majority 
have a sea green or drab ground color with a great variety of brown and 
lavender cloudings, spots, and blotches. It is but rarely that both eggs of a 
set are of the chocolate type. 
Three eggs in the Thayer colection are elliptical ovate in shape, 
smooth and somewhat glossy. One is “pale pinkish buff,” finely 
spotted over the entire surface and heavily blotched about the larger 
end with various shades of “sepia” and other dark browns, with 
numerous underlying spots of lilac and light drab. Another is light 
“buffy brown,” very finely sprinkled and conspicuously scrawled 
with the above colors. Still another is “wood brown,” finely . 
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