The Xantus Murrelet 



No. 296 



Xantus's Murrelet 



A. O. U. No. 25. Endomychura hypoleuca (Xantus). 



Synonym. — White-bellied Murrelet. 



Description. — Adult: Above and on sides (including axillars) slaty black, the 

 plumbeous tone faintly differentiated as skirting of feathers on back and wings; a touch 

 of white on either eyelid; below pure white, the lining of wings either pure white or 

 mingled in varying proportions with smoky gray. [Most published descriptions of 

 E. hypoleuca give "wing-lining pure white" as a diagnostic character, and the name 

 Endomychura (Brachyramphus) craveri (Salvadori) has been given to an alleged southern 

 form on the sole ground of smoky gray wing-lining. But the fact seems to be that 

 E. hypoleucus exhibits every degree of gradation from pure white to pure smoky. At 

 any rate, every variation within these limits is found off Monterey in winter. If this 

 be not the true explanation, then a new form having wing-linings of pure white and 

 characterized by a shorter beak must be set off from the bulk of mottled smoky-and- 

 white birds — and there is material in the Berkeley museum to support such a view.] 

 Bill black; iris brown; feet "whitish blue." No recognized seasonal changes. Downy 

 young: Above bluish black; below pure white. Bill black; feet paler. Measurements, 

 average of 10 Monterey specimens: length 246.8 .(9.72); wing 118.2 (4.65); bill 19.4 

 (.76), depth at angle of gonys 5.4 (.21) ; tarsus 23.7 (.93). 



Recognition Marks. — Robin size; black above, white below; amphibious habits. 

 Requires careful distinction from B. marmoratus (see under foregoing). 



Nesting. — Eggs: I or 2; placed at end of short burrow or in crevice or cave, or 

 under rock of sea-girt islet; variable in shade, and often exhibiting the most abrupt 

 diversity between "mates," dull white (rarely), olive-buff, greenish olive-buff and 

 pinkish olive-buff (avellaneous) to dull tawny olive or even dresden brown and cinna- 

 mon-brown; marked variously with purplish black, brownish black, deepest chocolate 

 or intense bister. Some specimens are nearly immaculate; in others the color is finely 

 and uniformly sprinkled over the entire surface; others are "cloud-capped" or hand- 

 somely wreathed about the larger end. Av. size 53.5x36 (2. 11 x 1.42); index 67.3. 

 Season: March— July; one brood. (The extremes of the season probably represent the 

 activities of diverse stocks or tribes.) 



General Range. — Coasts and islands of southern California and western Lower 

 California. Breeds sparingly as far north as Anacapa Island, and wanders further at 

 the close of the breeding season (?), probably as far as Tomales Bay (Nov. 10, 1910). 



Authorities. — Coues (Brachyramphus hypoleucus), Proc. Acad. Nat. Sci., 

 Phila., vol. xx., 1868, p. 64 (coast of Calif.) ; Beck, Proc. Calif. Acad. Sci., ser. 4, iii., 

 1910, p. 60 (Monterey Bay; occurrence; crit.) ; van Rossem, Condor, vol. xvii., 1915, p. 74. 

 figs, (crit.; relationship of hypoleucus and craveri); Howell, Pac. Coast Avifauna, no. 

 12, 1917, p. 22 (s. Calif, ids.; habits; occurrence, etc.). 



THE OPEN SEA is its home. Our little diver finds safety and food 

 far from land and the waiting enemy, the grim Duck Hawk. On or near 

 the surface it rides out storm or sunshine until darkness makes possible 

 a return to its island. 



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