BIRDS OF NORTH AND MIDDLE AMERICA. 

 CEPPHUS MANDTII (Mandt). 



MAHDT'S GUILLEMOT. 



737 



Similar to C). grylle, but greater wing-coverts white to extreme base 

 (sometimes with median basal portion dusky), the white wing-patch 

 wholly unbroken; size slightly less. 



Adults in hreeding plumage (sexes alike). — Uniform fuscous-black 

 or veiy dark fuscous, faintly glossed with greenish, especially on back, 

 scapulars, and rump; posterior lesser, middle, and greater wing- 

 coverts entirely white, (the feathers all white to extreme base) form- 

 ing a large, unbroken, and sharply defined patch on wing; axillars 

 and under wing-coverts (except along edge of wing) immaculate white ; 

 inner webs of primaries extensively white basally, except along shafts ; 

 bill black; inside of mouth vermilion red; iris dark brown; legs and 

 feet vermilion red, the claws blackish. 



Winter plumage. — Wings and tail as in summer; rest of plumage 

 pure white, the pileum, back, scapulars, and upper part of rump 

 variegated with black, the concealed and part of the exposed portion 

 of the feathers being black; legs and feet paler red. 



Young. — Similar to the winter plumage, but white wing-patch 

 broken by blackish tips to the feathers (their concealed bases white, 

 however), the secondaries and primary coverts with white terminal 

 spots, the rump and under parts indistinctly barred with grayish 

 dusky, and pileum with much less of black. 



Downy young. — Plain sooty blackish or dark fuscous, paler and 

 more grayish on under parts. 



Adult mcrZe.— Wing, 150.5-165 (158.1); tail, 40.5-51 (47.7); exposed 

 culmen, 28-33 (29.6); tarsus, 29-32 (30.6); middle toe, 33-38 (35.2). « 



Adult female.— Wing, 149-156.5 (153.1); tail, 44-51 (47.5); ex- 

 posed culmen, 28-31 (29.7); tarsus, 28-30 (29.4); middle toe, 33- 

 35.5 (34.2).^ 



(^ Eight specimeas. 



b Four specimens. 



40017— 19— Bull. 50, pt S- 



48 



