Mar., 1915 
NOTES ON MURRELETS AND PETRELS 
75 
between the two species so far as the under wing-coverts are concerned. It 
is hardly fair, however, to use no. 1 as typifying hypoleucus, as it has the dark- 
est wing lining I have ever seen out of a hundred odd birds handled in the 
flesh. Typical specimens with the wing lining immaculate are, on the Corona- 
dos at least, decidedly in the minority, most of the birds having concealed 
dusky bases to the feathers. In a dried skin this condition is not readily 
discernible, which may be the cause of the general belief that hypoleucus 
always has immaculate under wing-coverts. The unusual degree of clouding 
in the figured specimen is 
probably by reason of the 
immaturity of the bird. The 
coloration of the wing lin- 
ings of nos. 2-7 inclusive 
may be briefly described as 
a mottling of smoky brown, 
dark ashy and seal brown 
on a grayish white ground, 
except for the irregular 
spot near the base of the 
wing which is pure white. 
Of the specimens shown, 
nos. 2, 3, 6 and 7 are adults, 
and nos. 1, -1 and 5, birds of 
the year. However, as all 
have completed the fall 
moult (except for a few old 
summer feathers as noted 
farther on) it seems permis- 
sible to use adults and young 
alike for purposes of com- 
parison. Using, then, no. 1 
as representing B. hypoleu- 
cus and nos. 2-7 inclusive as 
examples of B. craveri, the 
following constant dissimi- 
larities (exclusive of the un- 
der wing-coverts) will read- 
ily be observed. The upper 
parts of the two species at 
first glance appear identical 
in shade and luster. Closer 
examination, however, shows 
craveri to be slightly but no- 
ticeably duller and browner 
on the sides of the face, neck 
and body ; moreover the dorsal plumage on being disarranged shows a decided 
brownish tendency, though this is obscured by the lighter tipping which is 
the same clear slate as in hypoleucus. The latter exhibits leanings in the same 
direction but in a much less degree, the brownish tinge being almost unnotice- 
able. A few old feathers still remaining unshed along the edge of the wing and 
on the shoulders of the adults would indicate beyond a doubt that the summer 
Pig. 27. Spring (left) and fall (right) specimens 
of Brachyramphus hypoleucus 
