38 . NORTH AMERICAN BIRDS. 



Upper parts rusty yellow, spotted with black; lower parts whitish gray. 

 Length 13.00-14.00, wing 10.10-11.15, tail 4.50-5.00 (forked for about .60- 

 1.00), culmen 1.00, tarsus 1.25, middle toe, with claw, about 1.25. Eggs 2-5, 

 1.78 X 1-26, ovate, or short-ovate, deep olive (varying in intensity, however), 

 rather indistinctly spotted or blotched with brown. Sab. Arctic regions; 

 in North America south, in winter, to New York, the Great Lakes, and 

 Great Salt Lake (casually to Bermudas and Peru). 



62. X. sabinii (Sab.). Sabine's Gull, 

 a'. Culmen nearly as long as tarsus ; tail forked for at least one and a half times 

 the length of the tarsus ; wing about 16.00 ; legs and feet red. (Subgenus 

 Greagrus Bonap.). Summer adult : Head and upper part of neck sooty slate, 

 with a whitish patch at base of bill ; mantle pearl-gray, the wing-coverts 

 and outer webs of scapulars whitish ; quills black, the shorter ones tipped 

 with white ; rest of plumage white ; bill black, with yellowish tip ; legs and 

 feet bright red. Young: Plumage generally, including head and neck, 

 white ; hind-neck, back, and scapulars, ashy brown, the tips of the feathers 

 margined with white ; tail-feathers (except outermost) with a black subter- 

 minal spot ; a dusky space immediately in front of eye, and another on ear- 

 coverts. Length about 23.00, wing 16.00, tail 8.00 (forked for about 3.30), 

 culmen 1.85, tarsus 1.90, middle toe, with claw, 2.00. Sab. Pacific coast of 

 South America ; Monterey, California ? 



— . X. furcata (Neb.V Swallow-tailed Gull. 



Genus GELOCHELIDON Brehm. (Page 24, pi. IX., fig. 4.) 



Species. 



Summer adult : Top of head and hind-neck deep black ; upper parts pale pearl- 

 gray, rest of plumage pure white ; bill deep black, feet blackish. Winter adult : 

 Similar, but head and neck white, the hind-neck tinged with grayish, the ear- 

 coverts and spot in front of eye darker grayish. Young : Similar to winter adult, 

 but upper parts washed with buff or clay-color, the top of head, hind-neck, back, 

 and scapulars sometimes streaked with dusky. Downy young : Above light gray- 

 ish buff, with several large and tolerably well defined dusky spots on hinder half 

 of head, a distinct dusky stripe down each side of hind-neck and upper back, the 

 wings, rump, and flanks with rather distinct large spots of dusky; lower parts 

 white, tinged with grayish on sides of throat ; bill brownish, inclining to orange (in 

 life) on lower mandible ; feet dull brownish orange (in life). Length 13.00-15.25, 

 wing 11.75-12.25, tail 5.50 (forked for 1.50-1.75), culmen 1.40, depth of bill at base 

 .45. Nest along sea-beach, in sand or shingle. Eggs 1.84 X 1-33, ovate, light bufly, 

 varying to pale olive-buffy, distinctly spotted and blotched with deep brown and 

 lavender-grayish. Sab. Nearly cosmopolitan; in America, Atlantic side, from 

 Brazil north to Long Island, casually to Massachusetts; very rare inland; both 

 coasts of southern Mexico and Central America in winter. 



63. G. nilotica (Hasselq.). Gull-billed Tern. 



