FUNCTIONS. 
223 
Albatross, flying at a greater elevation, satisfies itself, 
like the former, with what it can pick np from the 
surface of the waters. The Stormy Petrel sweeps close 
over the surface of the wave, feeding on minute 
molluscs and radiates, such as the smaller star-fish 
and Medusae, which are always to be found amongst 
the floating sea-weed. Their field of operation is the 
surface of the waters, and a slight depth under it; 
while the former go somewhat deeper. None of the 
Petrels dive. The Shear-water, however, can: it combines 
the Petrel with the Diver, and pursues both trades with 
equal ability. I may call it the most accomplished of all • 
sea-birds. 
There now remains for me to mention but one class 
of birds which gain their livelihood among the waters: 
I refer to the true Divers. Among these, the Grebes 
( Podiceps ) obtain their food with the least difficulty. 
They only dive in shallow water, and but few species 
among them are piscivorous; many feed on aquatic- 
plants, insects, and molluscs; some also catch insects in 
the air. The true Divers ( Colymbus ) are, on salt water, 
what the Grebes are on fresh, but are more given to 
catching fish. Lastly, the Guillemots and Auks 
( Mormon , Cephus , Uria , and Alca ): these are great 
catchers of shell-fish, star-fish, molluscs, worms, and 
other of the lower inhabitants of the sea. The Great 
Auk {Alca impennis ), which ranks with Penguins found in 
the South Polar Seas, may be regarded as a voracious 
fish, with a bird’s form and feathers. 
Thus, there is not a region of the earth, not the 
smallest spot, which does not afford nourishment for 
birds, whether it be the highest regions of air, or the 
lower depths of the waters; they are, one and all, 
