THE RHINOCEROS AUKLET. 907 
the infant is a showing of dull red near the middle of the otherwise black 
bill. The Puffin does not attain fully adult plumage until the second spring 
after hatching; while first year birds keep to sea and are never seen about 
the breeding haunts of the species. 
The Tufted Puffin nests to a slight extent upon the rocks and islands of 
the lower Sound, Williamson Rocks, Flattop, Bare Island, etc.; but the 
principal colonies are all within the Government reservations off the west 
coast. Alexander Island harbors in the neighborhood of 5000 birds, Erin 
2000, Wishaloolth as many, Cake Rock a goodly number, and Carroll between 
5000 and 10,000. A conservative estimate of the breeding population of 
the Olympiades would be about 25,000. 
No. 365. 
RHINOCEROS AUKLET. 
A. O. U. No. 15. Cerorhinca monocerata ( Pall.). 
Synonym.—Horn-BILLED AUKLET. 
Description.—A dults in breeding plumage: Upperparts sooty black or glossy 
brownish black, varied, especially on back, tertials, and rump, by sooty-gray tips 
of feathers; color of upperparts shading insensibly on sides of head, neck, and 
breast, into dull sooty-gray or smoke-gray of throat, chest, sides, and flanks; re- 
maining underparts white, or white faintly washed with smoke-gray; anterior 
margin of wing whitish; shafts of remiges whitish basally, in proportions decreas- 
ing from outermost; a maxillary and a post-ocular stripe of lengthened, lanceo- 
linear, white feathers; bill orange, duller along tomia, black on culmen, a horny 
projection above nostril at base of bill about .60 high (from nostril) ; a small 
deciduous plate at base of under mandible; feet and legs yellow above, black be- 
low; irides hazel. Adults in winter: Without horny appendage and_- infra- 
mandibular plate; irides white. Young of the year: Bill much smaller than in 
adult ; no white stripes on head; general plumage much as in adult in winter, but 
browner, and white of underparts washed or tipped with sooty-gray. Nestlings 
are covered with heavy slaty black down. Length of adult: 13.00-15.50 (330.2- 
393-7) ; wing about 7.00 (177.8) ; tail 2.35 (59.7); bill from base of horn to tip 
of culmen 1.13 (28.7); depth of bill including horn 1.10-1.25 (27.9-31.8) ; tarsus 
1.20 (30.5). 
Recognition Marks.—Teal size; horn (in breeding season) and white 
stripes of head distinctive in adult; dull plumage with size not likely to be con- 
fused in juvenile. 
Nesting.—Nest: at end of burrow driven 5-15 feet in perpendicular or slop- 
ing sea-wall. Eggs: 1, ovate, ovate-pyriform, or elliptical-ovate, dull white, im- 
maculate, or more commonly exhibiting traces of lavender, purple, or deep brown 
in spots or scrawls. Av. size, 2.70 x 1.80 (68.6x 45.7). Scason: May 1-June Io. 
General Range.—Coasts and islands of the North Pacific, north (at least) 
