1917 BIRDS OF THE SOUTHERN CALIFORNIA ISLANDS 23 
Rossem found the birds to be not uncommon in the same locality. One was shot 
by G. Willett (17) during November, 1907, at Santa Cruz Island. 
A. W. Anthony (23) states that on the Coronados in April, nearly all the 
eggs had hatched, but I have found fresh eggs in numbers the latter half of 
June, and a partly incubated set July 11, 1910. This might argue that two fam- 
ilies are raised each year, but as a number of eggs are broken against the hard 
rocks on which they are deposited, and as the mortality among the downy young 
must be considerable, I am inclined to think that the great proportion of hypo- 
leucus to be found nesting late in the season are birds whose first sets have come 
to grief. 
They do not assemble in colonies, but a number of pairs will often nest close 
together in some especially nice rock slide or other favorite location. Nests may 
be found from just out of reach of the high tides to the very tops of the islands. 
A real burrow is never constructed, nor will they inhabit one that is made by an- 
other bird, the usual site being a deep cranny under or between rocks and bould- 
ers. They will, however, enlarge a small crack between the ground and a rock, 
or scratch away a hollow in the loam beneath a tangle of low brush. No material 
is used for construction of a nest, and a surprising number of eggs are cracked 
by rubbing against the sharp rocks. Forty-eight hours elapse between deposi- 
tions of eggs, and these occur before six in the morning. 
A series of 152 eggs collected during the last few years by D. R. Dickey, A. 
van Rossem and myself, and measured by me, averages 2.10x1.41 inches. Ex- 
tremes are 1.93 to 2.30 inches in length, and 1.29 to 1.51 in diameter. No bird 
on the Check-List, possibly with the exception of those of the genus Uria, lay 
eggs exhibiting as wide a variation in color and markings as do those of Xantus 
Murrelet. Eggs even of the same set run from an almost solid dark chestnut to 
a clear sky blue with very faint markings. The majority have either a dark sea 
green or drab ground color, with a great variety of brown and lavender cloud- 
ings, spots and blotches. It is but rarely that both eggs of a set are of the darker 
type. D. R. Dickey has made a careful study of the sets of single eggs that occur 
so frequently, and he (1S) believes that the single eggs are incomplete sets, the 
parents of which have been killed, possibly by Duck Hawks, before the second egg 
was laid. Be that as it may, he has found only one incubated egg out of more 
than fifty sets of singles that he has examined, the remainder being either fresti 
or addled. This would indicate that the species practically never lays less than 
two eggs to the normal set. 
The young show amazing vitality. A set of two pipped eggs rescued by A. 
yan Rossem and myself after having been deserted among the cold, damp rocks 
by the parents thirty-six hours before, hatched two lusty youngsters, and these 
we succeeded in keeping alive for several days on a diet of hard-boiled eggs. 
When we substituted bits of fish for this, one died. The other escaped from his 
box, crawled out of the tent, tumbled down a cliff, and when discovered was 
making his way with all speed out to sea. The tarsus of a newly hatched chick 
is nearly as long as that of an adult, and they swim very fast, with their little 
feet fairly twinkling. Upon being placed in the sea at the age of two days, our 
bird at once made itself at home, diving at the slightest suspicion of danger and 
