The Cassin Auk let 



lid posteriorly; remaining underparts pure white. Bill (drying) black, changing to 

 yellow on base of lower mandible; iris greenish blue; feet chiefly black, nails black. 

 The fall moult renews and strengthens the plumbeous tone throughout, but the throat 

 is paler, sometimes definitely white. Immature: Similar to adult in autumn but wings 

 blacker. Feet and tarsi yellow before, black behind. Downy young: Chiefly brownish 

 dusky; white pattern of adult indicated by lighter gray on underparts; sides of head and 

 throat chiefly naked, orange-yellow. Bill and feet as in immature. Length of adult: 

 203.2-241.3 (8.00-9.50); wing 121. 9 (4.80); bill 19. 1 (.75); depth at base 9.9 (.39); 

 tarsus 25.4 (1.00). 



Recognition Marks. — Robin size; chunky appearance; stout bill; blackish and 

 white plumage; absence of appendages or special adornments in itself nearly dis- 

 tinctive, save as regards the slenderer and smaller-billed Marbled Murrelet. 



Nesting. — Single egg, white or pale greenish white, unmarked; placed at end of 

 burrow three or four feet in length, or in crevice of rock. Av. size 47 x 34 (1.85 x 1.34). 

 Season: April-June; one brood. 



General Range. — Pacific Coast and islands of North America from the Aleutian 

 Islands to the coast of northern Lower California, breeding throughout its range, or 

 perhaps retiring slightly in winter (at least to Cerros and Natividad Islands). 



Distribution in California. — Common resident on the ocean, and breeding in 

 suitable localities, chiefly the Farallons and the smaller islets along the entire coast. 



Authorities. — Gambel (Mergulus cassinii), Proc. Acad. Nat. Sci. Phila., vol. 

 ii., 1845, p. 266 (coast of Calif.); Stejneger, U. S. Nat. Mus., Bull. no. 29, 1885, p. 27, 

 footnote (molt of bill); Dawson, Condor, vol. xiii., 1911, p. 173 (Farallon Ids.; habits, 

 etc.); Howell, Pac. Coast Avifauna, no. 12, 1917, p. 20 (s. Calif, ids.) ; Bent, U. S. Nat. 

 Mus., Bull. no. 107, 1919, p. no (life hist.; desc. and photos of nests, etc.). 



THE PETREL population of the islands lying off the coast of Cali- 

 fornia is not large; and Howell is probably correct in his surmise 1 that this 

 species outnumbers all our other small pelagic birds combined. The 

 case was quite otherwise on the coast of Washington, where in 1907 we 

 had just discovered the presence of Cassin Auklets on a rocky islet which 

 was tenanted by some 40,000 Beal Petrels. 



Determined to get a line on the night-life of this interesting colony, 

 we returned to the mainland for blankets and other supplies and had the 

 Indians land us by canoe at nightfall. The distant lights of the Indian 

 village and the myriad stars entertain us, but the real performance does 

 not begin till well on toward ten o'clock. Now for the orchestra. "Pet- 

 teretteretterell, etteretteretterell"- - it is the tap, tap of the Petrel conductor 

 calling the island to attention. Soon ghostly forms steal about in the 

 gathering gloom. Voice answers voice as each moment flies. The flitting 

 shadows become a throng, and the chorus a tumult. But in the grand 

 melange there is a new note. A quaint, burring croak wells up from the 

 ground, elfish, gruesome, portentous. The Cassin Auklets are waking 

 up. Heard alone, the Auklet chorus reminds one of a frog-pond in full 



1 A. B. Howell. Pac. Coast Avifauna, No. 12, (1017), p. 21. 

 I468 



