hunger, the robber soon abandons his usual precautions: he
suddenly dashes into the living mass; but, attacked from all
sides, he again is compelled to retreat. From sheer despair he
falls upon the wild ducks; but the intelligent, social birds
rapidly gather in a flock and fly away if the robber is an erne;
they plunge into the lake if it is a falcon; or they raise a
cloud of water-dust and bewilder the assailant if it is a
kite.(2) And while life continues to swarm on the lake, the
robber flies away with cries of anger, and looks out for carrion,
or for a young bird or a field-mouse not yet used to obey in time
the warnings of its comrades. In the face of an exuberant life,
the ideally-armed robber must be satisfied with the off-fall of
that life.

Further north, in the Arctic archipelagoes,

"you may sail along the coast for many miles and see all the
ledges, all the cliffs and corners of the mountain-sides, up to a
height of from two to five hundred feet, literally covered with
sea-birds, whose white breasts show against the dark rocks as if
the rocks were closely sprinkled with chalk specks. The air, near
and far, is, so to say, full with fowls."(3)

Each of such "bird-mountains" is a living illustration of mutual
aid, as well as of the infinite variety of characters, individual
and specific, resulting from social life. The oyster-catcher is
renowned for its readiness to attack the birds of prey. The barge
is known for its watchfulness, and it easily becomes the leader
of more placid birds. The turnstone, when surrounded by comrades
belonging to more energetic species, is a rather timorous bird;