76 
THE CONDOR 
Vol. XVII 
plumage of these specimens was very different from that of B. hypoleucus, these 
feathers being of a shade about intermediate between hair brown and seal 
brown. In this regard it may he appropriate to mention that I have never 
seen any breeding specimens of hypoleucus that are clear slaty. A slight 
brownish east is apparently always present, most decided on the wing quills 
and tips of the scapulars though the whole .dorsal plumage is slightly suffused 
particularly in the more worn specimens. In the case of nos. 2-7 the unicolored 
feathers on the sides of the body and flanks greatly outnumber the variegated 
ones, while with hypoleucus the exact opposite is the case. The general effect 
is much the same, in other words in both species the parts mentioned have a 
mottled appearance, hut from a different cause. An individual feather in the 
case of craveri is, when followed up, usually found to he either dusky or Avhite, 
and the mottling results from the intermingling of these feathers, but in 
hypoleucus the same effect is obtained (generally speaking) by reason of the 
individual plume being bicolored. 
Aside from the smaller feet and hills no differences are discernible 
between the two birds of the year and the four adults (of B. craveri ) except a 
more blackish cast to the dorsal plumage apparently by reason of the tipping 
being of a slightly darker shade. Figure 27 will give a good idea of the differ- 
ence in shade between the breeding and fall plumage of Xantus Murrelet. 
To sum up the situation, nos. 2-7 may be referred to />. craveri for the fol- 
lowing reasons : 
B. hypoleucus B. craveri 
Wing lining immaculate or nearly so. 
Concealed portions of dorsal plumage 
with faint brownish cast. 
Side of head, neck and body blackish 
slate. 
Unicolored feathers on sides of body in 
minority. 
Worn summer feathers light slaty with 
faint brownish suffusion. 
Wing lining heavily clouded and mottled. 
Concealed portions of dorsal plumage with 
strong brownish cast. 
Sides of head, neck and body brownish 
slate. 
Unicolored feathers on sides of body in 
majority. 
Worn summer feathers about intermediate 
between hair brown and seal brown. 
The petrel colony on Los Coronados is, I am happy to state, apparently 
gaining in numbers each year. Messrs. Grinnell and Daggett on their visit to 
the Islands, August 6 and 7, 1902 (Auk, XX, 1903, pp. 27-37) make no esti- 
mate of the numbers of either Socorro ( Oceanodroma socorroensis) or Black 
( Occanodroma melania ) petrels breeding there at that time, hut state that 
twenty-four adults of the former and four of the latter species together with 
many young and eggs were taken in an afternoon’s hard work. From what 1 
have seen there the present season, it would now he rather a simple matter 
for two persons to obtain upwards of fifty adult Socorro Petrels in the same 
length of time on the same date. This refers to the main colony; but small 
branch colonies have sprung up wherever sufficient soil is available to burrow 
in. In many instances this year no burrow at all ivas dug, the birds simply 
worming their way under the dense bushes to lay their eggs. 
Another matter of surprise to me is the fact that Messrs. Grinnell and 
Daggett found socorroensis breeding on North Island, a condition which is cer- 
tainly non-existent at the present time, though melania nests there in consid- 
erable numbers. Possibly the hordes of Cassin Anklets ( Ptychoramph us aleu- 
ticus) which infest the island in the breeding season, as well as a mouse ( Pero - 
my sc us sp.) which also abounds there, have at last driven socorroensis to take 
refuge on the smaller Middle Island, which place now seems to be their sole 
