NORTH AMERICAN BIRDS. 33 



the larger end, but, like the eggs of all terns, are extremely variable. 

 The average size is 1.75x1.30. 



This is the only species of tern having the bill shaped in a noticea- 

 ble degree like that of a gull — hence its common name. 



Marsh Tern is another name by which it is known, but this is not 

 regarded as exactly correct. 



According to the best authorities the Gull-billed Tern is a species 

 of wide distribution and is characteristic of no particular region, breed- 

 ing alike in the islands of the Indian Ocean and in those of the Gulf 

 of Mexico, the islands and the coasts of Jutland in Denmark and 

 along the coast and the interior in the marshes and lagoons of southern 

 South America. A few specimens have been taken on the coasts of 

 France and Germany, and it is recorded as being common in Hun- 

 gary, Greece, and Asia Minor, where it breeds. 



It is known to breed in various other portions of Southern Europe, 

 and also in the northern parts of Africa. Its flight is spoken of as easy 

 and graceful, partaking of the elegance which is characteristic of these 

 birds when on the wing. 



64. Sterna tschegrava Lepech. [680.] 



Caspian Tern. 



Hab. Nearly cosmopolitan; in North America breeding southward to Virginia, Lake Michigan, 

 Texas, Nevada and California. 



This is the largest of these elegant and graceful birds, the Terns ; 

 it measures from twenty to twenty-three inches in length. The bill of 

 this bird in life is of dark vermilion-red, growing lighter towards 

 the tip ; the pileum and occipital crest is glossy, greenish-black, ex- 

 tending to the lower line of the eyes. The back and upper parts 

 of wings are pearl-blue, the whole underparts are white. The legs 

 and feet are black. The extent of wings in the adult bird is from fifty 

 to fifty-five inches. It is nearly cosmopolitan in its distribution, being 

 found in greater or less abundance in various portions of the globe. 



At a distance it is often mistaken for the Royal Tern, but may be 

 distinguished from the latter by its more robust form and less deeply 

 forked tail. 



The bird is also known as the Imperial Tern ; irregularly distributed 

 throughout North America , but chiefly in the Arctic regions, where it 

 .breeds, and along the entire Atlantic coast. Eggs and young have 

 been taken on Cobb's Island, Va., in July. Dr. Merrill observed it 

 breeding on Padre Island, near Fort Brown, Texas, in May. Mr. B. 

 F. Goss found it nesting on the islands of Eake Michigan. Earge 

 numbers of this species are said to breed on Pelican Island in the 



