690 STERNA DOUGALLI, EOSEATE TERN. 



is nearly pnro black, lightening a little at the tip. The davt portion of the feathers 

 grows lighter on each successively, until the inner ones are very light pearl — so light 

 as to appear to fade insensibly iuto the white Avhich broadly margins them. The sec- 

 ondaries are white, with the greater part of their outer and a small part of their inner 

 ■webs pearl-blue. The tail is exceedingly short, measuring less than four inches, the 

 amount of emargin.ation being only one inch, or even less. The outer pair of rectrices 

 are narrower than the others, but hardly longer than the next pair, and not more 

 acutely pointed. The rectrices are pearl-blue, darkest on their outer vanes, so light as 

 to be almost white on their inner. The outer web of the outer feather, however, is not 

 so dark as the next. Toward the extremities of the rectrices there is a subterminal 

 border of brownish-black extending around the tip, and for half an inch or more down 

 on e'lch .side. External to this rim of black there is another, which ends the feather, 

 of pure or yellowish white. The markings of the tail are abrupt and well defined. 

 The legs and feet are dull greenish-black, like the bill, with a shade of reddish 

 slightly apparent over some of the joints ; the soles inclir ing to yellowish, the claws 

 black, with whitish tips. Length of tarsus, 0.75 ; middle toe and claw, 0.90. The 

 ground color of the upper parts is a very light pearl-blue, much as in the adults, and 

 is pretty pure and uninterrupted on the rump and greater wing-coverts. But on 

 the back, the hind neck between the shoulders, the scapulars, tertials, median coverts 

 and inner secondaries, this color Is almost completely obscured and hidden by a very 

 beautiful, fiue, delicate, continuous mottling of black and light yellowish or fawu- 

 color. This black is disposed chiefly in narrow, irregular, zigzag transverse lines, but 

 their continuity everywhere interrupted by the mottling of fawn-color. TLis appear- 

 ance is very difficult to describe ; it is quite unlike anything else I have seen among 

 Terns, and rather reminds one of the delicately but inextricably blended colors of a 

 Scops, a Caprimulgns, or perhaps of some Scolopacince. On the tertials, inner secondaries, 

 inner longest coverts, the pattern of mottling becomes larger and more distinct, for 

 the feathers are, toward their termination, almost wholly black, with yellowish borders. 

 The head is as peculiar as the back. The forehead and cheeks are of a uniform, deli- 

 cately blended, and soft, light grayish-brown, which on the vertex and occiput becomes 

 resolved into small, broad, indistinct longitudinal stripes of quite deep black and dull 

 fawn-color, the streaks again being lost on the nape in perfectly uniform dull blackish. 

 Just before and above the eye there is a spot almost pure silvery white ; the eye is en- 

 circled by nearly pure black, aggregated into a pretty well-defined semiluiie before it, 

 stretching out behind it as an extensive spot, covering the auricular and temporal 

 legions ; pretty sharply defined with the white below ; being insensibly blended with 

 the color of the occiput above. The under parts are pure white ; but on the sides of 

 the breast, or quite across it, the extreme tips of the feathers are a little obscured by 

 dusky, causing them to appear exactly as if .soiled. There is the ordinary band along 

 the edge of the fore-arm of dull black, but it is obscured by some light fawn-colored 

 tips of the feathers. 



Dimensions of the adult. — Length, 14 to a little over 15 inches; extent, about 30 ; 

 wing, from carpus, 9J to 9f ; tail, 7i to 7| ; depth of fork, :i-J to 4-J- ; bill, aloug culmen, 

 1.50 ; from nostrils to tip, 1.25 ; from feathers on side of lower mandible to tip, 1.75 ; 

 height at hose, 0.35; gonys, 1; rami, 0.75; tibia3 bare, 0.40; tarsus, 0.85; middle toe 

 toe alcne, 0.75 ; its claw, 0.25. 



Dimensions of young-of-year. — Length, average, about 11 inches ; extent, 28 ; wing, 

 from cai-pus, 9.25; tail averaging 4 inches, with a depth of forliiug only 1 to 1^; 

 length of bill, 1.35; its other dimensions, and those of the feet, correspondingly less 

 than in the adult. (Compare also measurements given in the description of the young- 

 of-the-year before the first moult.) 



Though of about the same size as the typical species of Sterna, its form is more slen- 

 der. The bill is relatively longer, slenderer, more acute, with a but slightly convex 

 culmen, f.nd the gonys longer than, instead of about equal to, the exposed portion of 

 the rami. The wings are shorter, with less tapering and acute tip. The relative 

 length and attenuation of the exterior rectrices surpasses that of auy other species of 

 Sterna. The tibiae are bare for a considerably shorter space. The claws are remark- 

 ably arched, especially that of the outer toe. In the pattern of coloration it adheres 

 more closely to the type, though the bill is black and the pilenm of a diflferent shape 

 and degree of persistency in winter. No other species of bterna proper has so marked 

 a roseate tint on its under parts, it being in this respect, for its genus, what galericulata 

 is for " Thalasseus," 



The bill of perfectly adult birds is pure black, except the extreme base, which, with 

 the mouth, is bright red. In immature specimens of various ages it is, for a greater 

 or less extent toward the base, light-colored, with considerable of a vermilion or 

 rather light carmine tint during life. In others the whole bill is pure black. I have 

 never seen it, however, so largely red as it is represented to be in Audubon's plate. 

 The other variations, beyond those normal and constant ones of age and sea' on above 

 detailed, consist chiefly in a greater or less elongation of the tail. 



It is impossible to confound this species, in mature summer plumage, with any other 



