222 
BIRD-LIFE. 
floating on the surface of the water; they rarely 
capture anything alive: they are the true Bavens 
and Crows of the ocean. These are surpassed, in every 
respect, by the Terns, which elegant creatures under¬ 
stand the art of diving, from a height, to perfection. 
While the Marsh Terns (. Hydrochelidon ) are especially 
insectivorous, the Sea Terns ( Sylochelidon ) are more 
given to fishing, and some dive with much rapidity, 
even to a considerable depth. The Gannets alone are 
capable of surpassing them in this respect, seizing 
fish, as they do, at a depth of six feet below the 
surface. 
The structure of the feet places the Gannets among 
the Pelicans; they are distinguished, however, from 
the former, chiefly by their mode of gaining a liveli¬ 
hood. Pelicans fly easily and well, but cannot dive; 
they fish only in shallow water, for which operation 
their drag-net-like pouch is especially adapted. Cor¬ 
morants, on the contrary, are indifferent flyers, but 
can dive to a depth of perhaps thirty ells to catch 
fish, and manage to swim with the same ease and 
rapidity as their prey. The Darter earns its daily bread 
in a similar manner. This bird swims with great 
activity under the surface of the water in pursuit of 
its prey. Lastly, the Frigate-bird combines diving from 
a height with diving while swimming; it can fly and 
dive almost with equal facility, and obtain its living on 
the surface of, as well as under, the water; 
The Petrels are, to a great extent, obliged to confine 
their operations to the surface of the water. The Stormy 
Petrel ( Procellarict ) follows the course of the billows, 
dropping in a curve upon them, when it picks up 
anything that it finds floating upon their surface. The 
