LABIDM—LABIN^ : GULLS. 741 



Smaller: length about 24.00 inches; wing 17.00 or less ; bill about 2.00 j tarsus 2.25 ^euco^terus 769 



Mantle light blue; primaries the same, with definite white tips gla/ucescen& 770 



Mantle very pale blue, as in te!«!Oi)«ents/ primaries with slate-gray markings . . . , kvmlieni 770a 

 £. Very large: mantle slaty-blackish; primaries crossed with black; size of the first . . marinus 771 



C, Large : mantle some shade of blue, darker than in A, lighter than in B; primaries crossed with black. 



Mantle grayish-blue ; bill moderately robust ; feet flesh-colored argentatus or amithsonianus 772, 773 



Mantle slaty-blue; bill very robust; feet flesh-colored occidentalis 774 



Mantle dark grayish-blue ; bill moderately robust ; feet yellow ; eyCTring orange . caclmmcms 775 

 Mantle dark slate; bill moderately robust; feet flesh-colored affinis 776 



D. Medium and small : primaries crossed with black; feet dark-greenish; webs yellow. 



Tarsus obviously longer than the middle toe and claw ; bill of adult greenish-yellow, encircled 

 with a black band; first primary usually with a sub-apical white spot ; length about 18.00-22.00 



delawarensis 778 

 Tarsus little if any longer than middle toe and claw ; bill with a red spot, but an imperfect black 

 band, if any; first primary usually with the end broadly white; length about 20.00-22.00 



eaUfomicus 777 

 Tarsus little if any longer than the middle toe and claw ; bill slender, greenish, without ^ black 

 band or red spot ; size very small ; length 16.00 or 18.00 . . . canus or brachyrhynchus 779, 780 

 II. Tail and under parts darkin adult. Head white; bill and feet reddish. (Blasipus.) 



Back slaty-lead color Iteermcmni 781 



■j-es. L. glau'cus. (Gr. yXavKos, glaukos, 'LbA. glaucus, bluish.) GLAUCOUS Gull. Ice Gull. 

 Burgomaster. Very large : length about 30.00 ; extent 60.00 ; wing up to 18.50 ; bill 2.75- 

 3.00 (chord of culmen), along gape 3.75, its depth opposite nostrils 0.80, at angle 0.85 ; tarsus 

 3.00-3.25 ; middle toe and claw 2.75. No black anywhere at any age. Adult $ 9 : BiU large 

 and strong, very wide, but not so deep at angle nor so convex at end as in marinus, about as 

 long as middle toe and claw ; chrome yellow, the tip diaphanous yellow, a vermilion spot at 

 the angle. Legs and feet pale flesh-color or yellowish. Iris yellow. Primaiies entirely white, 

 or palest possible pearly-blue, fading insensibly into white at some distance from their tips, their 

 shafts straw-yeUow. Mantle very pale pearl-blue. Otherwise, wholly white. In winter : 

 Head and hind neck lightly touched with pale brownish -gray. An immature stage : Entirely 

 white ; bUl flesh-colored, black-tipped. Young : Bill flesh-colored, black-tipped ; plumage 

 impure white, mottled with pale reddish-brown, sometimes quite dusky on the back ; under 

 parts a nearly uniform pale shade of brownish ; quills and tail imperfectly barred with the same. 

 Smaller: wing 17.50; bill 2.40 ; tarsus 2.40, etc. Northern and Arctic seas, circumpolar ; S. 

 in winter in N. Am. to the Middle States, coastwise ; breeds only in the high north. This is one 

 of the very largest and most powerful birds of the whole family, fuUy equalling L. marinus in 

 these respects. 



769_ li. leucop'terus. (Gr. Xev/cdr, kucos, white; irrepSv, pteron, wing.) White-winged Gull. 

 Precisely like the last, but smaller. Length 24.00, rather less than more ; wing 16.00-17.00 ; 

 bill along culmen 1.75-2.00, along gape about 3.75 ; depth at angle 0.65 ; tarsus 2.00-2.25, 

 not longer than middle toe and claw. This counterpart of L. glaucus inhabits the same north- 

 erly regions, coming south to the same degree in winter. It appears to be much less character- 

 istic of N. Am. than of Europe. 



iyyQ_ li. glauces'cens. (Lat. glauceseens, growing bluish.) Glaugous-winged Gull. Like a 

 herring gull with the black of the primaries washed out ; primaries of the color of the mantle 

 to the very tips, which are occupied by definite small white spots ; the 1st also with a large 

 white sub-terminal spot. Bill long and rather weak, the upper mandible acute and projecting 

 considerably beyond tip of the under, the convexity near the end comparatively slight ; angle 

 pretty well defined, the outline between it and the tip about straight. Tarsus rather longer 

 than middle toe and claw. Length about 27-00 ; wing 16.75 ; bill along culmen 2.25 ; 

 gape 3.25 ; depth at angle 0.70 ; tarsus 2.60 ; middle toe and claw 2.50. Adult in summer : 

 Bill light yellow, an orange spot at angle of lower mandible, and a dusky one just above. 

 Mandible pearl-blue, much the same shade as in a/rgentatus. Primaries scarcely darker than 

 the back, all with well-defined, rounded apical spots of white. First, the base not appreciably 



