LIIE HISTORIES OF NORTH AMERICAN GUIJL.S AND TERNS. 233 



recfular scrawls. These markings are in the darker shades of brown, 

 such as " chestnut brown," " burnt umber," or " seal brown." Some 

 eggs have underlying blotches of lighter shades, such as "tawny- 

 russet " or " hazel." Nearly all eggs, especially the lighter types, 

 show spots or blotches of various shades of lilac or lavender grays. 

 Where there are markings of several different colors on the same 

 egg the effect is often very pretty. The measurements of 65 eggs, in 

 the United States National Museum, average 43 by 31 millimeters; 

 the eggs showing the four extremes measure 48 by 29.5, 43 by 33.5, 

 39 by 31 and 42 by 28.5 millimeters. 



Young. — The period of incubation is 23 days, and probably both 

 sexes incubate. The young remain in the nest for a few days, until 

 they are strong enough to run about or swim, when they become very 

 lively and pugnacious. They take to the water readily and soon 

 become expert at running or swimming about the marsh and hiding 

 in the grass. They are fed by their devoted parents until fully 

 grown and able to fly. 



Plumage. — The downy young is quite different from that of the 

 common tern. The upper parts vary from light "clay color," 

 through "cinnamon buff" to "pinkish buff," shading off to paler 

 shades of the same color below, paling on the breast and belly almost 

 to white, and darkest on the throat, which is "wood brown" or 

 " drab " in some specimens, but never so dark as in the common tern. 

 The upper parts are heavily spotted or streaked with black or 

 " blackish brown," less heavily on the head and more heavily on the 

 back, where these markings are confluent into great blotches or longi- 

 tudinal bands. This color pattern is well adapted to conceal the 

 chick among the lights and shadows of the marsh grass where it 

 hides. 



The Juvenal plumage, which is acquired by the time that the young 

 bird has attained its growth, is also quite distinctive and matches the 

 surroundings in which the young bird lives with a heavy suffusion 

 of dark browns on the upper parts. In this plumage the pearl 

 gray of the back and scapulars is almost wholly concealed by the 

 brown terminal portions of the feathers, which are " clay color " or 

 "cinnamon buff," centrally clouded or barred with "snuff brown," 

 or "burnt umber"; the top of the head is nearly uniform "snuff 

 brown " ; the sides of the neck are heavily clouded, and the forebreast 

 and rump are lightly clouded with the same color, which also shows 

 on the tips of the lesser wing-coverts, some of the greater wing- 

 coverts, and the rectrices ; a conspicuous black patch surrounds the 

 eyes and covers the auriculars. As the season advances all these 

 brown markings fade or wear off to produce the first winter plumage ; 

 in this plumage the rump and breast become pure white, the browns 

 on the upper parts gradually disappear or leave only traces of the 



