LIFE HISTOBIES OF NORTH AMERICAN GULLS AND TERNS. 209 



Food. — The Caspian tern secures its main food supply, which con- 

 sists almost wholly of small fish, by plunging headlong into the 

 water, often disappearing entirely under the surface. It probably 

 feeds to some extent on shrimps and other forms of surface swim- 

 ming aquatic life. Dr. P. L. Hatch (1892) says that its favorite 

 food is "the fresh-water mussels, with which the margins of the 

 marshland streams and lakes abound," while on its spring migration 

 in Minnesota. Several writers have stated that it feeds on the eggs 

 and young of other birds, a gull-like trait not shared by the other 

 terns. 



Behavior. — The flight of the Caspian tern is strong, swift, and 

 graceful, but heavier and more gull-like than that of the smaller 

 terns. Its general manner of flight is, however, decidedly tern-like, 

 as it flies along in search of food, with its bill pointed downward, 

 pausing to hover for an instant and then plunging vigorously down 

 into the water. When fishing it usually flies only a few yards above 

 the water, but when traveling it flies at a great height, with its bill 

 pointing straight forward, making rapid progress, even against a 

 strong wind. It has a broad expanse of wing, and is more given to 

 soaring than the other terns. I have seen it soaring in great circles, 

 mounting higher and higher in the air, as the gulls are wont to do. 

 it so closely resembles the royal tern that the illustrious Audubon 

 never detected the difference, but it can be recognized by its heavier, 

 more stocky build, by its heavier flight, by its shorter and less 

 deeply forked tail, and by the larger amount of black in the 

 primaries, which look wholly black when seen from below, whereas 

 those of the royal tern seem to be largely white or grayish. 



The cry of the Caspian tern is entirely unlike that of the royal 

 tern and quite different from that of any of the Laridae. Its or- 

 dinary note is a hoarse, croaking " kraaa " on a low key, loud, harsh, 

 and grating. A shorter note sounding like " kow " or " kowk " is 

 often heard on its breeding grounds, where it also utters, when 

 angry, a loud, vehement, rasping cry of attack. 



On its southern breeding grounds, where it is usually larger and 

 stronger than its associates,' it has few enemies. It has been said to 

 eat the eggs and young of other birds, but I have never seen any 

 evidence of this habit, and I believe that it seldom, if ever, attacks 

 them. Audubon (1840), however, saw some evidence of its pug- 

 nacity on the Labrador coast. He says: ° 



Until that period I was not aware that any tern could master the Lestris 

 Pomarinm, to which, however, I there saw the Cayenne tern give chase 

 driving it away from the islands on which it has its eggs. On such occasions 

 I observed that the tern's power of flight greatly exceeded that of the jasrer- 

 but the appearance of the great black-backed gull never failed to fill it with 



