BIRDS OF NORTH AND MIDDLE AMERICA. 565 
and pointed, the longest primary (outermost) exceeding distal sec- 
ondaries by more than half the length of the wing. Tail two-fifths 
as long as wing or a little more, truncate or slightly emarginate. 
Tarsus relatively short, much shorter than middle toe without claw 
(decidedly shorter to very slightly longer than exposed culmen), 
the planta tarsi not serrate or roughened; hallux absent or rudi- 
mentary, if present very minute and without claw; webs between 
anterior toes full, scarcely if at all emarginate anteriorly. 
Coloration.—Adults with head, neck, rump, tail-coverts, tail, and 
under parts immaculate white; back, scapulars, and wings plain 
bluish gray, the primaries with black and white “pattern” on distal 
portion; in winter, the white of occiput, nape, and sides of chest 
overlaid or clouded with color of back; young with a black patch 
across hindneck, in one species with part of lesser wing-covert area 
and a band across tip of tail also black. 
Range.—Circumpolar regions, south, in winter, to Mediterranean 
and Caspian Seas, Bermudas, and coasts of United States to about 
35° N. (Two species.) 
KEY TO THE SPECIES AND SUBSPECIES OF RISSA. 
a. Without black on hindneck. (Adults.) 
b. Legs and feet blackish; exposed culmen 34-49. (Rissa tridactyla.) 
c. Hallux usually obsolete; smaller, except feet (averaging: Male, wing 312.7, 
tail 128.4, culmen 38.7, tarsus 34.1, middle toe 41.1; female, wing 299.4, 
tail 121.2, culmen 34.1, tarsus 31.5, middle toe 36.1). (Northern Atlantic 
and adjacent portions of Arctic Ocean.)..Rissa tridactyla tridactyia (p. 565). 
cc. Hallux usually obvious, often distinct though minute; larger, except feet 
(averaging: Male, wing 323.6, tail 135.1, culmen 40, tarsus 33.9, middle toe 
40.9; female, wing 320.6, tail 131.3, culmen 39.1, tarsus 33.7, middle toe 
40). (Northern Pacific Ocean, Bering Sea, and adjacent waters.) 
Rissa tridactyla pollicaris (p. 571.) 
bb. Legs and feet red (yellowish in dried skins); exposed culmen 28-31.5. (Bering 
BOB. )accsiescaccceaienseae setae seme mamanamennes Rissa brevirostris (p. 573). 
aa. With a black patch on hindneck. (Young.) 
6. Anterior lesser wing-coverts and band across tip of tail black. 
Rissa tridactyla tridactyla, young (p. 566). 
Rissa tridactyla pollicaris, young (p. 571). 
bb. Without any black on lesser wing-coverts or tail. 
Rissa brevirostris, young (p. 573). 
RISSA TRIDACTYLA TRIDACTYLA (Linnzus). 
KITTIWAKE. 
Adults in summer (sexes alike).—Head, neck, rump, upper tail- 
coverts, tail, and entire under parts, including axillars and under wing- 
coverts, immaculate pure white; back, scapulars, wing-coverts, and 
secondaries plain light gray (between light and pale neutral gray), on 
the secondaries passing into white terminally; primaries paler gray 
(pale neutral gray), the five distal ones with their terminal portion 
black, this color extending for about 82-83 mm. on the outermost (the 
