AN ESSAY ON BIRD-MIND 123 



when the bird is full of energy and outer conditions 

 are favourable, gives pleasure. The best-know^n 

 example is the song of song-birds. This, as Eliot 

 Howard has abundantly shown, is in its origin and 

 essential function a symbol of possession, of a nesting 

 territory occupied by a male — to other males a notice 

 that * trespassers will be prosecuted,' to females an 

 invitation to settle, pair, and nest. But in all song- 

 birds, practically without exception, the song is by no 

 means confined to the short period during which it 

 actually performs these functions, but is continued 

 until the young are hatched, often to be taken up 

 again when they have flown, or after the moult, 

 or even, as in the Song Thrush, on almost any sunny 

 or warm day the year round. 



And finally this leads on to what is perhaps the 

 most interesting category of birds' actions — those 

 which are not merely sometimes performed for their 

 own sake, although they possess other and utilitarian 

 function, but actually have no other origin or raison 

 d'etre than to be performed for their own sake. They 

 represent, in fact, true play or sport among ourselves ; 

 and seem better developed among birds than among 

 mammals, or at least than among mammals below the 

 monkey. True that the cat plays with the mouse, 

 and many young mammals, like kittens, lambs, and 

 kids, are full of play ; but the playing with the mouse 

 is more like the singing of birds outside the mating 

 season, a transference of a normal activity to the plane 



