CLASS II. AVES: OEBER 8. NATATORES. 341 
THE TROPIC BIRD. 
within the tropics ; many of them breed on the rocky islands at the east end of Porto Rico, and 
some on the Bermudas. They feed entirely on fish, which they capture by descending upon 
them and seizing them in their bills. The Smithsonian Catalogue mentions the Yellow-billed 
Tropic Bird, P. flavirostris, found in the tropical regions of the Atlantic seas. There are sev- 
eral other species in the Indian and Pacific Oceans. 
THE LAEID^ OE GULLS. 
This family includes the Terns or Sea-Swalloios, the Shearzoaters, and the Ti-tie Gulls. All 
these birds have long wings, fly with great ease, and spend a great part of each day in hovering 
over the sea, generally along the shores, in search of food. They often sit on the water, where 
they are very buoyant, but they swim little, and are incapable of diving. They are active, noisy 
birds, mostly living on small fish, which they capture in skimming over the water. 
Genus STERNA : Sterna. — This includes several species of Tern. The Common Tern of 
Europe, S. hirundo, is fourteen inches long; ash-gray above, beneath white; builds sometimes on 
rocky and sometimes on low, flat, sandy islands, but always near the sea ; eggs two, of a yellowish 
stone-color. Like the swallows of the land, it flies with great ease, and is almost the whole day on 
the wing, noisy, and restless, performing various graceful evolutions in the air, yet constantly 
looking out for the small fish on which it feeds. This species is chiefly confined to the seas of Eu- 
rope ; in winter it migrates tb the southern latitudes. 
Other species are as follows: the Arctic Tern, S. Arctica; found in Europe and America; 
the Whiskered Tern, S. leitcopareia, found in Europe : the Gull-billed Tern, S. Ayiglica ; found 
in Europe and North America : the Marsh Tern — S. aranea of Wilson ; found on our Atlantic 
coast: the Lesser Tern, S. minuta, a very elegant species ; found in Europe, India, and the 
United States : the Black Tern, S.fissipes, common in Europe and America : the White-winged 
Tern, S. leucoptera, a handsome species with a long tail ; found in Europe ; the Sooty Tern, S. 
fuliginosa, possessing a remarkable power of flight ; found in Europe, Asia, Australia, and America; 
and the Roseate Tern, jB'. Douglassi ; found in Europe and America. 
