292 Field Museum of Natural History — Zoology, Vol. IX. 



Adult in winter: Similar, but with head and neck streaked and 

 spotted with brownish gray; tail feathers marked with more or less 

 dusky; bill, yellowish. 



Immature: Bill, dull flesh color, the terminal third, black; general 

 plumage mottled and streaked with gray and pale brown, the feathers 

 on the back margined with gray; primaries, dark brown. 



Length, 22 to 25.50; wing, 16.20 to 17.50; bill, 1.90 to 2.50; 

 greatest depth of bill, .70 to .85. 



The Herring Gull is common on Lake Michigan in winter and dur- 

 ing the migrations and is often seen on the Lake near Chicago. It 

 breeds in Wisconsin. 



"Very abundant winter resident upon Lake Michigan and occurs 

 throughout the state." (Nelson.) "As a rule it is found in winter 

 throughout Illinois and thence southward to the Gulf of Mexico." 

 (W. W. Cooke.) "Very common" on Lake Michigan at almost all 

 seasons and a common migrant on all suitable waters of the state of 

 Wisconsin. Nests commonly on different islands of Green Bay and 

 on the north shore of Lake Michigan." (Kumlien and HoUister, 

 Birds of Wisconsin, 1903, p. 9.) 



It breeds in May or early in June. The nest is composed of grass 

 and moss on the ground or rocks (very rarely in trees). The eggs 

 are from 2 to 3, pale olive brown, blotched and lined with chocolate 

 brown, and measure about 2.80 x 1.90 inches. 



17. Larus delawarensis Ord. 



Ring-billed Gull. 



Distr.: Nearly the whole of North America, south in winter to 

 Mexico and Cuba. 



Adult in summer: Back and wing coverts, pearl gray; terminal 

 portion of inner primaries, black, tipped with white; terminal portion 

 of first primary, black, with large white spot near the tip; head, tail, 

 and under parts, white; bill, greenish yellow, with a black band. 



Adult in winter: Similar, but having the head and neck streaked 

 with gray; black band on the bill much less distinct. 



Immature: General plumage, whitish, more or less mottled and 

 streaked with gray and brownish gray ; tail feathers marked with more 

 or less brownish black, forming a broad, irregular black band with 

 narrow white tips; primaries, blackish, only the inner ones tipped 

 with white; bill with basal portion, brownish yellow and the entire 

 end from the nostril, black. 



