54 THE STORY OF- THE BIRDS: 
of self. But society interests were also developed, in 
which every individual was made in some sense his 
brother’s keeper. Wonderful social instincts were 
organized among insects, fishes, birds, and mammals. 
With these came voluntary social calis, so frequently 
noted in the chirps of birds. These naturally grew 
out of mother calls and nestling cries for food, and 
out of their little by-talks. 
But Nature was not content yet! An individual 
might forget his social duties, as many individuals 
have. Where these are necessary for the good of 
the race she has made them involuntary. She has 
fastened them upon external features so indelibly 
that a mother unconsciously calls her young and a 
frightened member of a flock mechanically warns and 
guides his following fellows. She has made altruism 
automatic by habits crystallized in structure and by 
calls and cheers that are dyed in color. In some 
cases she has made the bird almost literally “ wear his 
heart upon his sleeve.” 
Usually these are on fleeing, flocking, defenseless 
creatures. Antelopes are social, crepuscular, depend- 
ing on flight for safety, and usually have a leader. 
They are conspicuously white in the rear, that those 
following the weaker brothers may be guided into 
safety. The mother hides her young, and, returning 
to it, presents a broad white breast mark as a maternal 
signal. Similarly the deer hoists a white tail, and the 
cottony patch of the rabbit answers the same purpose. 
But the hare’s is a sadder story. Now he is soli- 
tary and selfish. Once he was (like the European 
