LABID^—STEBNINJE: TERNS. 157 



792. S. (G.) an'gUca. (Lat. anglica, Anglican, English.) Gull-Billed Tern. Marsh Tern. 

 (J 9 ) iu summer : Bill rather shorter than head, robust, not very acute, compressed ; cnlmen 

 nearly straight to beyond nostrils, then very declinato-convex to the tip ; gonys about straiglit ; 

 rami slightly concave ; symphyseal eminence well marked ; tomia of lower mandible inflected ; 

 conmiissure gently curved. Heiglit of bill at base a third of total length. Nasal groove 

 short and broad, not deep ; nostrils short, widely oval, placed very near base of bill, just 

 beyond the termination of the feathers. Wings exceedingly long and acute, each primary 

 surpassing the next by a full inch ; the secondaries short, soft, obliquely incurved at their 

 extremities. Tail short, contained 2i times in the wing; deeply emarginate, but its lateral 

 feathers not elongated nor attenuated. Feet long and stout for this subfamily. Tarsus 

 shorter than bill, longer than middle toe and claw. Hind toe remarkably developed ; inner 

 shorter than outer; interdigital membranes deeply incised, especially the inner. Tibia naked 

 for half an inch. Crown and long occipital crest glossy greenish -black, extending on to lower 

 border of eye, leaving only a very narrow line of white to run along the edge of the feathers 

 on side of upper mandible. Neck all round and under parts, white. Mantle light pearl- 

 blue, this color extending on rump and tail, quite to the tips of the rectrices; tail-feathers, 

 indeed, deepest colored at their tips, fading into nearly pure white toward their bases, on that 

 portion of each feather which is covered witli the next one. The color of the mantle extends 

 quite to tips of tertials, but dilutes a little toward the tips of the secondaries. Shafts of 

 primaries yellowish-white. Primaries all grayish-black, deepest on the outer vane of the 

 first ; but this color so heavily silvered as to appear umch lighter. All the primaries have 

 on their inner webs a space of white, which extends toward their apices for a varying distance 

 on each ; on the first the white is largest, purest, and extends furthest ; is distinctly defined 

 from the black, and has not a margin of black along its inner border, except just at its apex. 

 Tlie amount of the white diminishes in length and breadth with each successive primary, 

 until on the last one it is inconspicuous ; stUl it is quite perceptible on all. Bill black, 

 with or without a minute yellowish tip ; legs and feet greenish-black ; iris brown. In muter : 

 Differs in restriction of the black cap, chiefly to the hind head and nape, on sides of head 

 reaching forward to eye ; sometimes extinct, except in dusky eye-stripe and spot before eye, 

 wlien whole head otherwise white. Young: BUI blackish-brown, pale at base below; feet 

 dull brownish. Upper parts pearl-blue, interrupted by numerous crescentic or hastate spots 

 of dull brownish, one on each feather, the extreme tip of which is whitish. A brownish- 

 black bar along lesser wing-coverts. Forehead and most of crown white, with dark shaft- 

 lines, increasing to exclude white on hind head and nape ; blacldsh spot before and behind 

 eye. Neck all around, upper tail-coverts, and whole under parts, white. Tail-feathers 

 whitening at ends, each with a dusky space. Length 13.00-15.00; extent 33.00-37.00; 

 bill 1.40; along gape 2.00; its height at base 0.45 ; tibiae naked 0.50; tarsus (average) 1.30; 

 middle toe and claw 1.10; hind toe and claw 0.40; wing 11.75-12.25; tail 5.50, forked 

 1.20-1.75. Nearly co.smopolitan ; in N. Am., not abundant, and chiefly in Eastern U. S., 

 Texas to New England. Not a beach-nester ; breeds in marslies, like the black tern ; 

 eggs 3, laid on broken-down reeds or grasses, 1.75 X 1-30, olivaceous, largely and irregularly 

 splashed with umber-brown and blackish, especially about the largest part, but very variable, 

 like all terns' eggs. 

 793. S- (T.) cas'pia. (Of the Caspian Sea. Fig. 512.) Caspian Tern. Imperial Tern. Of 

 maximum size. Length 20.00-23.00; extent 50.00-55.00; wing 15.00-17.00, usually about 

 16.00 ; tail only 5.00-6.00, forked about 1.50, middle feathers broad to their rounded ends, rest 

 growing successively more acute, but lateral without any slender filamentous development. 

 Bill extremely large, 2.75 along culmen, 4.00 along gape, 0.90 deep at base, 0.50 wide at 

 nostrils ; about as long as head, with culmen regularly curved from base to tip ; outline of 

 mandibular rami slightly concave ; gonys about straight ; angle not very weU marked. 



