112 DIVISION I. VERTEBRAL ANIMALS.—CLASS II. AVES. 
the sunken rocks below, as this harmless wanderer, whose manner informs 
them of the approach of the storm, and thereby enables them to prepare 
for it.” The Petrels are nocturnal birds. When, therefore, they are seen 
flying about and feeding by day, the fact appears to indicate that they have 
been driven from their usual quarters by a storm; and hence, perhaps, arose 
the association of the bird with the tempest. Though the Petrels venture 
to wing their way over the wide ocean as fearlessly as our swallows do over 
a mill-pond, they are not, therefore, the less sensible to danger; and, as if 
feelingly aware of their own weakness, they make all haste to the nearest 
shelter. When they cannot then find an island or rock to shield them from 
the blast, they fly towards the first ship they can desery, crowd into her 
wake, and even close under the stern, heedless of the rushing surge, so that 
they can keep the vessel between them and the unbroken sweep of the wind. 
Faumy Lartpz. Guys, Skuas, AND TERNS. 
The Gulls proper frequent the shores of the ocean, but often wander to 
great distances from land ; they are incapable of diving, but swim buoyantly. 
Their food consists principally of fish and crustacea ; but some of the larger 
species feed occasionally on the flesh of cetaccous animals, and devour the 
young and eggs of some species of sea-birds. These birds vary much in 
size, some being quite small, while others rank among the largest of marine 
birds. They are not peculiar to any region, but are found abundantly over 
the world. They congregate in great numbers on the sand-bars at the 
entrance of inlets and large bays. In winter they migrate in search of 
food, frequenting harbors, and ascending rivers. 
Nearly resembling the Gulls proper are the Skua-gulls, or Jwgers. 
These hardy birds inhabit the high latitudes of both hemispheres. There 
are four arctic species, found both in Europe and North America. They are 
piratical in their habits, appearing to derive their subsistence mainly from 
the labors of others. They chase and harass various species of gulls, com- 
pelling them to disgorge a portion of their food, which they dart after, and 
seize before it reaches the water. 
The Terns are mostly found on the sea-coast and neighboring bays, ocea- 
sionally on rivers and lakes; they assemble in large numbers on the sand- 
bars and points at the mouths of inlets, are much on the wing, and are 
remarkable for their buoyant and easy flight. Their food consists of small 
fishes and crustacea, which they obtain by hovering over and suddenly dart- 
ing down upon. Although they thus seize their prey while in the water, 
they only occasionally swim or rest upon its surface. These birds are so- 
ciable in their habits, congregating in large communities in the breeding 
season, and nesting near each other on the ground. 
