THE RHINOCEROS AUKLET. 907 



the infant is a showing of chill 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 ne\er seen about 

 the breeding haunts of the species. 



Tlie 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 reser\ations oflf 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 conserxative estimate of the breeding population of 

 tlic C)lympiades would be about 25.000. 



No. 365. 



RHINOCEROS AUKLET. 



A. O. U. \o. 15. Cerorhinca monocerata (Pall.). 

 Synonym. — Horn-billed Auklet. 



Description. — Adults in brccdinq phimagc: Upperparts sooty black or glossy 

 brownish black, varied, especially on back, tertials, and rump, by sooty-gray tips 

 of feathers ; color of upperparts shading insensiblv 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 witli 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 ]:)Iate at base of under mandible ; feet and legs yellow above, black be- 

 low ; irides hazel. Adults in ivintcr: \\'ithout hornv appendage and infra- 

 mandibular plate; irides white. Yonnc/ of the year: Piill 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. I^ength 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. — Xcst: at end of burrow driven 5-15 feet in perpendicular or slop- 

 ing sea-wall. Eggs: i, 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 ('68.6x45.7). Season: May i-June 10. 



General Range. — Coasts and islands of the Xorth Pacific, north (at least) 



