228 EVOLUTION OF BIRD- SONG 



admitted by most naturalists. But no individual 

 bird has ever been known to radically change its 

 colours, even under the influence of the most com- 

 plete change in its surroundings ; yet, as we have 

 seen, many song-birds exhibit such a change in their 

 songs to an extent patent to all who have paid 

 attention to the subject. Is it strange, then, that a 

 woodpecker should have a cry exactly like the note 

 of its neighbour a tree-frog (see p. i88), whose cries 

 may be a survival of the complainings of the permian 

 epoch ? ^ Is it wonderful that in autumn the brown 

 wren should particularly affect a little chirp (not the 

 love-call-note) like the chirp of its companion at that 

 season, a cricket, whose note may have first been 

 produced by an orthopterous ancestor in the coal 

 period ? Can we wonder that the young of the 

 imitative butcher-bird, when out of the nest, should 

 squeal like a tortured frog or bird, when we know 

 that the parents slay frogs and birds in the vicinity 

 of the young ? It is but natural that the blackbird, 

 which in winter so often hears the curious toneless 

 bubbling sounds audible when one holds a cracked 

 snail close to the ear, should terminate its song with 



^ I shall never forget the loud shrilly noise made by some so-called 

 " tree-frogs " at Ceres, Cape Colony. In March 1885 they produced, 

 every night, quite a din, rendering conversation under the trees a matter 

 of some effort. 



