220 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



over the speculum ; just after the moult, when the feathers are entirely 

 fresh, the ends of the middle coverts will usually conceal the black bar — 

 although it mos-tly shines through — but later in the season the overly- 

 ing tips are worn away and the cross-bar becomes visible; at all events 

 it can bo seen by gently x)ushing the middle coverts a little aside, as 

 there is no need of lifting tbeni up in order to detect the black bases of 

 the underlying feathers. On the other hand, no abrasion or removing 

 of the middle coverts will ever produce anything like the dark cross- 

 bar in C. mandtii.* The stoutness and slenderness of the bill as coin- 

 cident with the presence or absence of the cross-bar is very marked. 



There is no difficulty, then, in telling the old birds apart, as they are 

 distinguishable at a mere superficial glance. Adult birds in winter 

 l)lumagc have also the speculum pure white, that is to say, without 

 blackish or dusky spot and mottlings at the tip of the feathers. These 

 are only moulted once a year, and are consequently the same as those 

 of the l)lack summer plumage; the character is therefore just as well 

 marked in the winter garb. In the young birds a little more caution 

 and closer inspection are needed, and, in fact, there is usually more dark 

 color at the base in these than in the adults (Figs. 5, 6), but in all speci- 



Fig. 4. Ce2>phus cnlumba, ,]uu. Fig. 5. Cep'phus grylle, jnu. Fig. 6. Cepi)hus mandtii, inn. 



mens of the large number before me the characteristics of the two 

 forms are well expressed, not a single reference of a specimen is ques- 

 tionable, and I doubt whether specimens i-eally are found which are 

 not easily attributed to the one or the other species. 



The young mandtii has the tips of the primary coverts and of the 

 secondaries more or less broadly edged with white, which is said never 



*It is only just to mention that the v.ilue of this character was not first pointed out 

 by Professor Newton, as he and others have thought, for Brehm, in his original des- 

 cription of U. f/lacialis (1824), mentions it in very explicit words. He says (Lehrb. 

 Eur. Vog., p. [)2')) : "The long upptr wing-coverts are white to their very base, and 

 therefore no black cro.ss-bar is jiroduced on the wing of tbe old l)ird (one may push 

 the feathers aside ever so much) like that in the two foregoing species" [ U7'ia grylle 

 and Uria arctica Buehm]. 



