770 SYSTEMATIC SYNOPSIS. — LONGIPENNES— GA VIJE. 



315. HYDROCHELI'DON. (Gr. vhap, Jnulor, water; x^^^^'^^t chelidon, a swallow.) Black 

 Terns. Bill a little sliorter than head, longer than uiiddle toe and claw; very delicate, slender, 

 acute ; culmeu and commissure decidedly decliuato-convex, the amount of curvature increasing 

 toward the tip; outline of rami and gonys both concave, the former most so; eminentia sym- 

 physis prominent and very acute. Wings exceedingly long, pointed, of same color as hack, 

 without distinct markings on either web. Primaries broad and not very tapering, not acute ; 

 tertials very short, rounded, not slender nor flowing, reaching in the folded wing only half-way 

 to tip of longest primary. Tail rather short, contained 24 times in the wing, only moderately 

 emarginate (much as in Geloehelidon) , the lateral feathers but little exceeding the next, not 

 tapering and acuminate ; all the feathers broad and rounded. Feet slender and short ; tarsi 

 much abbreviated, rather less than the middle toe alone. Toes moderately long ; the webs 

 rather narrow and very deeply incised (fig. 51). Size small, general form delicate; colors 

 mostly black, the wings and |ail plumbeous. 



Analysis of Species, 



Wings and tail above like back lariformis 806 



Wings whitening along border of forearm; upper tail-coverts white leucoptera 807 



806. H. larifor'mis. (Lat. lariformis, gull-shaped.) Black Tern. Short-tailed Tern. 

 Adult, in summer : Head and neck all around and under parts to the vent, jet black ; under 

 tail-coverts pure white. On back of neck, and between shoulders, the black lightening into 

 leaden-gray, which extends over all the upper parts to the very tips of the tail-feathers. Ter- 

 tials like back ; secondaries darker, tending to the color of the primaries, which are grayish- 

 black, silvered, wMi paler margins of inner webs, their shafts white except at tips. Lining of 

 wings ashy-white, reaching a little over border on to lesser coverts. Bill and claws black, 

 angle of mouth lake red ; feet reddish-brown ; eyes brown. In winter : Very different ; fore- 

 head, sides of head, neck all round, and entire under parts, white ; under wing-coverts only 

 ashy-gray. Upper parts generally as in summer, but paler, many feathers with whitish edges. 

 A grayish -black bar along lesser coverts. On the crown, white varied with grayish or ashy, 

 darker on nape, with bar through eye. While changing, head and under parts patched with 

 white and black. Young : Bill brownish-black, base below flesh-color ; mouth yellow ; feet 

 light brown. Forehead grayish-white, deepening on crown and nape to grayish-brown which 

 reaches down to the back, obscuring the plumbeous ; interscapulars quite brown ; on other 

 upper pai-ts the brown edges the feathers. Lesser -^^g-coverts grayish-black. A black cres- 

 cent before eye. Under parts pure white, the sides of the breast ashy-brown, the sides of the 

 body and lining of the wings ashy. Quills as in the adults, but the shafts of the primaries 

 brown. Length about 9.25; e.xtent 25.00 ; wing 8.25 ; tail 3.75, forked 1.00 ; bill along cul- 

 men 1.10 ; along gape 1.60 ; height at base 0.25 ; gonys 0.60. Young smaller, about 8.00 ; 

 bill 1.00 ; tail shorter and less forked. N. Am. at large, interior and coastwise, abundant. 

 Breeds in large colonies anyivhere, in marshes and reedy sloughs, in June. Eggs on debris Oi 

 dead reeds, often wet and floating, without any nest; 2-3, 1.35 X 0-95 average, pointed, yet 

 with considerable bulge of the sides ; ground color brownish-olive, rather pale and clear, 

 thickly marked with spots and splashes of every size from dots to masses, but mostly large 

 and bold, of light brown and blackish-brown, and the usual neutral-tint sheU-markings ; ten- 

 dency to aggregate at or around the larger end. 



807. H. leuco'ptera. (Gr. XfijKof, ?e?(A'o.s, white ; wTepoi/, pteron, -wing.) White-winged Black 

 Tern. Adult in summer: Bill black, tinged with red; feet red; claws black. Head and 

 neck all around and under parts pure black, slrading on back and scapulars into dark slaty 

 plumbeous ; wings dark silvery-plumbeous, fading to white along border of forearm, the quills 

 silvered-dusky with white shafts and dull white area on inner webs of the primaries ; lining of 

 wings sooty blackish, varied with white along the border. Tail and its coverts, above and 



