14 Bird-Song : and New Zealand Song Birds 
is certainly instinctive.” Hudson (HN, pp. 89 et seq.) shows 
that at least the understanding of the significance of certain 
cries is instinctive. The Rev. W. Herbert, on the other hand 
(WS, note on pp. 131-2), makes very full observations on the 
learning of song by young birds, the gist of the observations 
being against the song being instinctive. 
It may be that the knowledge of the song does lie deep 
within—unexpanded—in a bud, as it were, which opens in 
response to the throbbing of the song of the species; so that 
the free young bird adopts the song that finds the readiest 
echo in its own breast. Young birds vary in the docility shown 
in learning the song of other birds—see Witchell (WE, 
pp. 175-6), Wood (WW, p. 59), Bolton (BH, vol. 1, pp. 11, 30, 
56)—the acquired song smothering or partially smothering, 
the natural song. The young cuckoo shows no docility what¬ 
ever, but on leaving the nest responds to the natural song 
of its kind. 
Human song gives wide expression to the emotions of love, 
of praise, of joy, of good-fellowship. It surely would be too 
much to say that the source of the whole is in the sexual 
emotion, the songs of worship and good-fellowship being 
merely secondary blossomings of the primary emotion; rather 
it would be nearer the truth to say that song is a natural 
expression of emotion, the expression being most developed, 
most exuberant, when the spring-tide of the blood is flowing; 
and that in song the sexual emotion finds a powerful ally, 
seizing upon it, but not creating it. for the furthering of its 
own especial and occasional end. That which is true of human 
song is true, in a larger degree, of bird-song; nor does this 
ascribe to birds a greater aesthetic sense than has alreadv been 
ascribed to them by those who maintain their song is purely 
sexual. 
Most of the songs recorded in the following chapters have 
been heard many times. There was never any doubt about the 
simpler phrases. Those with enharmonic intervals have been 
taken down, put by, taken down again at intervals of weeks 
or seasons, and compared,—until there is no doubt whatever 
