[Illustration]
Anti-social activities of humans such as those of brigands who plunder
their fellow men find their parallels in the bird world.
The bald eagle is one of the best-known of the birds that practice
such brigandage. Fond of fish, and capable of capturing it himself
upon occasion, it is a common practice for the eagle to take fish from
the osprey, plunder the osprey has just caught from the water. The
osprey, with a fresh-caught fish, flies heavily. The watching eagle
quickly overtakes the smaller, heavily laden bird and forces it to
drop its catch, then dives down and usually catches the fish before it
can strike the land or water. Rarely does the osprey escape with its
food under such an attack. It is recorded that an eagle made several
dives at one fish-laden osprey and, when these were not successful in
making it lose its hold on the fish, the eagle dived under the smaller
bird, turned over on its back, and with talons outstretched, snatched
the fish from the grasp of the osprey and sailed away with it, as
successful a pirate as ever sailed the seas.
NEMESIS OF VULTURES Besides taking fresh-caught food from the osprey
the bald eagle has been seen pursuing vultures and making them disgorge
their meal of carrion. The eagle, if unsuccessful in catching the
disgorged food in the air, may land on the ground and eat it there.
We know also that the aerial flights the eagle uses to frighten the
vulture into relinquishing his food are not idle threats, for an eagle
has been seen to strike and kill a bird that refused to disgorge.
Not only does our American eagle adopt such practices, but related
species in other parts of the world behave in similar ways. The New
Guinea sea eagle harries the osprey there, and on the west coast of
Africa a sea eagle robs pelicans and cormorants of their prey.
Certain long-winged birds of the tropical seas, such as _Fregata
magnificens_, are known popularly as man-o'-war birds or frigate
birds, reflecting their well-known character as pirates and tyrannical
freebooters. The man-o'-war birds get part of their food from many
creatures which swarm at the surface of the sea, but they also get much
of their food by forcing terns, cormorants, boobies, and pelicans to
deliver up their catch.
In a tropical bay a school of small fish comes to the surface, perhaps
driven by large fish below; from far and near terns gather, darting
down to seize the fish that jump into the air. Above them circle the
frigate birds, ready to dive down and chase and harry a successful tern
until it drops its fish and leaves its prey to the freebooter.
BOOBIES ARE VICTIMS Frigate birds may sail about, also, where a colony
of nesting brown boobies is located, waiting for the birds laden with
food to return home. When such a food-laden booby returns, the frigate
bird dashes down at it, buffets it with its wings, snaps at it with
its long, hooked bill, until the booby finally drops its fish for the
man-o'-war bird to enjoy.
The skua, a big, dark relative of the gull, is also known as a pirate.
Its chief food is fish but it also eats many other foods from the
sea. It rarely takes the trouble to fish for itself but watches until
some other bird, perhaps a gull or a tern, has been successful in
its hunting and then gives chase, forcing the unfortunate hunter to
relinquish its food. Several of the skua's smaller relatives, the
jaegars, have similar habits. It is written of the pomarine jaegar off
our New England coast that they are notorious pirates and freebooters,
the highwaymen among birds that prey on their neighbors on the fishing
grounds and make them stand and deliver. The jaegar gives chase to a
tern that has caught a fish and follows it through every twist and turn
as if the two were yoked together. Finally the harassed tern drops its
fish and the jaeger swoops down and seizes it before it can strike the
water.