88 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4TH SER. 
month. The July and August birds, however, appear to be 
mere loiterers out of health. Visitors from the breeding 
grounds do not begin to arrive in force before October. In 
November and during winter they often become very com- 
mon, but they are extremely irregular, and even a season may 
pass with few or none being met with. Usually the dark 
phase greatly outnumbers the light. In 1904, Mr. Beck found 
Fulmars common as late as April 15. 
The Academy’s series of two hundred and fifty-seven Pacific 
specimens, chiefly from the vicinage of Point Pinos, California, 
throws considerable light on the various plumages assumed by 
this species. 
It is made evident by this series that Fulmarus rodgersi 
Cassin is merely a nominal species. The intergradation is 
complete between birds of the light phase having the upper 
parts smoky gray, lighter on top of head and hind neck, and 
birds having mantle, tail, and inner webs of primaries almost 
wholly, white. 
In my second paper on California water birds, attention was 
called to an extreme example of the light phase from San 
Francisco Bay having the mantle entirely white.» According 
to Dr. Godman, “occasionally pure white individuals are met 
with’” on the North Atlantic, evidencing that the whitening of 
the mantle is not confined to birds breeding in the vicinity of 
Bering Strait. 
As specimens of the Academy’s series grade from appar- 
ently immature birds into those with the white mantle, it is 
probable in the light phase that the whiter birds are the more 
aged. This, however, can not be proved conclusively from 
available material, collected as it has been on the ocean remote 
from breeding stations, with no examples showing the transi- 
tion from the natal down to the definitive feathers. In short, 
it apparently remains to be determined by specimens whether 
the birds of the light phase grow whiter with age or whether 
they pass from the natal down to the various aspects of that 
phase without intermediate stages; with age eliminated, there 
would then remain dichromatism and geographic variation as. 
possible factors. 
1 Proc, Calif. Acad. Sci., 2d ser., v. 6, p. 27. 
2Mon. Petrels, p. 267; see also pl. 77. 
