578 Eepoet of State Geologist. 



following are the measurements of three of tHe eggs, representing the 

 amount of vaiiatioii: 1:70 by 1.25, 1.75 by 1.20, 1.S8 fey 1.25. The 

 grotLdd color varies from pale greenish to warm, brownish-drab. Tke 

 spots and shell markings are of a varying shade of brown, distributed 

 much as in the other terns' eggs." 



16. (70.) Sterna hirundo Linn. 



Gommon Tern. 



Synonyms, Sea Swallow, Wilson's Term. 



Adult in Summer. — Similar to S. forsteri, but with the outer web. 

 of outside pair of tail feathers grayish or dusky, the inner web wiiita; 

 below, pale gray or grayish-white, whitening on the throat, and white 

 on erissum; bill, red, blackish toward the tip; feet, red, lighter than 

 bill. Adult in Winter. — Similar, but with forehead and crown white. 

 Immature. — Similar, but the crown with more or less grayish; the 

 upper parts with more or less bufEy or brownish; tail, shorter; bill, 

 brownish. 



Length, 13.00-16.00; wing, 9.75-11.75; tail, 5.00-7.00; depth of 

 fork, 3.50; biU, 1.25-1.50. 



Eange. — ^Korthem part of Northern Hemisphere. In America, 

 breeding locally from Florida and Arizona to Arctic coast. Winters 

 from Virginia to Bermudas and Lower California. 



Eggs, 2-3, generally deposited in a depression in the sand, varying 

 from greenish to deep brown, spotted and blotched with brown, 

 blackish, and lilac, 1.62 by 1.24. 



, . Migrant; in some localities abundant. Some remain throughout 

 the summer in the northern part of the State, where it may breed. 

 These birds are later arriving in the spring and earlier returning in 

 the fall than the last mentioned species. I have no record earlier 

 than May 2, and generally it is the latter part of the month when 

 they are chiefly noted. They seem to . mark the end of the spring 

 migrations. I noted one on the "Whitewater River, June 3, 1884, 

 which is the latest spring record for the southern part of the State. 

 They leave for the south in August. It has been reported from Franklin 

 County, Carroll and Marshall (Evermann), Monroe (Bollman), Allen 

 (Stockbridge), Putnam (Earlle), Steuben (Cass), Laporte (Barber). 

 Lake (Parker, Meyer and Tallman-). This species is the common tern 

 of the Atlantic coast, but Forster's is more common in the interior. 

 They are said to breed at St. Clair Flats, on Heisterman's Island, in 

 Saginaw Bay, "on muslfrat houses in marshes," and in the Upper 



