248 BIRDS OF ILLINOIS. 



upper parts, including lower part of the nape, upper tail-coverts, and tail pale pearl-gray, 

 deepest on the dorsal region and wings. Two to three outer primaries dusky slate, the 

 inner webs broadly edged with white ; remaining quills pale pearl-gray, like the coverts, 

 the edge of the inner webs white. Entire lower webs pure white. Bill bright yellow, usu- 

 ally (but not always) tipped with black; iris dark brown; legs and feet bright orange-yellow. 

 Adult, in winter: Similar, but lores, forehead, and crown grayish white (purer white ante- 

 riorly); an occipital crescent and a stripe forward from this to and surrounding the eye 

 blackish. Bill dusky; legs and feet dull yellowish. Young, first plumage: Somewhat 

 similar to the winter plumage, but humeral region marked by a wide space of dusky slate, 

 the scapulars and interscapulars with sulmarginal V- or U-shaped marks of dusky, the 

 crown streaked and the occiput mottled with dusky, and the primaries darker than in the 

 adult. Bill dusky, brownish toward the base; feet brownish. Downy young: Above, 

 grayish white, flnuly mottled with dusky grayish, the head distinctly marked wiih irregular 

 dots o'. dusky black; lower larts entirely immaculate white. Bill dull yellow, tipped with 

 dusky; legs and feet clear pale yellow. 



To;al length, about 9.00-9.40 inches; e-ictent, 18.75-20.00 ; wing, 6.60; tail, 3.50, its fork. 1.75; 

 culmon, 1.20; depth of bill at base, .28; tarsus, .60; middle toe, with claw. .72. 



This beautiful little tern occurs in summer nearly througliout 

 the Mississippi Valley, and, doubtless, breeds somewhere within 

 the limits of Illinois, although there is not, to my knowledge, 

 any record of its doing so. It is much more abundant along 

 the Atlantic coast, where it formerly bred regularly as far north 

 as Massachusetts, but on account of the increasing summer 

 population of the localities most frequented by it (the islands 

 just off the coast), it, like other terns, is said to be growing 

 every year less numerous, and has even quite abandoned many 

 of its former breeding grounds. 



' Its habits are quite similar to those of other species of the 

 same genus. It is equally bold and pugnacious when its eggs 

 or young are menaced, when it keeps up a protesting cry of 

 «///, uik', ut'Ji', sounding very much like the querulous grunt 

 of a young pig whose mother has left it too far in the rear. 



Its eggs are deposited on the bare sand, gravel, or "shingle" 

 beyond reach of the highest tides, and in color assimilate so 

 closelj' to their .surroundings as to be with great difficulty 

 detected . 



Genus HYDROCHELIDON Boik. 



I/ydroc eddon BoiE, Isis, 1822, 503. Type, Sienia iiiara Linn. 



Gek. Chab. Similar to the smaller species of Sterna, but tail only very slightly forked 

 or emnrginate, the rect rices not attenuated at ends, and the webs of the toes flUing loss 

 thanhalf the intmdigital spaces. Adults gray or blackish beneath, as dark as, or darker 

 than, the color of the upper surface. 



