284 
ANIMAL INTELLIGENCE. 
on or flying over the surface of the water, the gulls wait 
till a guillemot comes to the surface with a fish, and then 
v/rest the latter from the beak of the former. In the 
robber-tern this instinct has proceeded further, so that the 
animal gains its subsistence entirely by plunder of other 
terns. I have often observed this process, and it is inte- 
resting that the common tern well knows the appearance 
of the robber ; for no sooner does a robber-tern come up 
than the greatest consternation is excited among a flock 
of common terns, these flying about and screaming in a 
frantic manner. The white-headed eagle has also de- 
veloped the plundering instinct in great perfection, as is 
shown by the following graphic account of Audubon : — 
During spring and summer, the white-headed eagle, to procure 
sustenance, follows a different course, and one much less suited 
to a bird apparently so well able to supply itself without inter- 
fering with other plunderers. ISTo sooner does the first hawk 
make its appearance along the Atlantic shore, or around the 
numerous and large rivers, than the eagle follows it, and, like a 
selfish oppressor, robs it of the hard-earned fruits of its labour. 
Perched on some tall summit, in view of the ocean or of some 
watercourse, he watches every motion of the osprey while on 
the wing. When the latter rises from the water, with a fish in 
its grasp, forth rushes the eagle in pursuit. He mounts above 
the fish-hawk, and threatens it by actions well understood; when 
the latter, fearing perhaps that its life is in danger, drops its 
prey. In an instant the eagle, accurately estimating the rapid 
descent of the fish, closes its wings, follows it with the swiftness 
of thought, and the next moment grasps it. The prize is carried 
off in silence to the woods, and assists in feeding the ever- 
hungry brood of the eagle. 
The frigate pelican is likewise a professional thief, 
and attacks the boobies not only to make them drop the 
fish which they have newly caught, but also to disgorge 
those which are actually in their stomachs. The latter 
process is effected by strong punishment, which they con- 
tinue until the unfortunate booby yields up its dinner. 
The punishment consists in stabbing the victim with its 
powerful beak. Catesby and Dampier have both observed 
and described these habits, and it seems from their account 
that the plunderer may either commit highway robbery in 
