10 Bird-Song : and New Zealand Song Birds 
(TB, p. 149 et seq .—quoting from Newton’s Dictionary). It 
would appear to be altogether a mating and brooding song; 
but there are modifying facts to follow. The thrush, on the 
other hand, sings through the greater part of the year; and 
other birds, such as the robin and the water-ousel, sing during 
autumn as well as summer; and on this fact Darwin comments 
(DD, p. 370), “nothing is more common than for animals to 
take pleasure in practising whatever instinct they follow at 
other times for some real good.” From the other point of 
view it might be said, Nothing is more common than for the 
sexual instinct to seize and use as incentive some quality that 
at all times gives pleasure. 
Is it a sexual instinct that impels the male birds to precede 
the females in their migration? The males of most of the 
summer wood-warblers appear as much as a fortnight before 
the females (WAY, p. 59), and immediately commence their 
song. The song is at first immature, gradually reaching its 
full perfection during the time the males are alone (CAY, pp. 
115-16). It is hardly likely that they sing without experienc¬ 
ing pleasure from their song, even in the absence of the females: 
can it be supposed that their pleasure is heightened by antici¬ 
pation? Have they anything of the human emotion whereby 
We look before and after; 
We sigh for what is not? 
It is probable that the song is an indication of the awakening 
and the stirring of sexual emotions, as the scent of the flower 
is an indication that it is ready for the touch of the pollen- 
grains ; but the song comes with the emotions, not because of 
them—or why are so many birds songless? It is during this 
period of probationary song that the birdcatchers trap the 
nightingale. The birds then caught may be trained to become 
fine songsters; but if, after the arrival of the females, a male 
be trapped whose singing has secured him a mate, not only 
will he be of no use as a cage song-bird, but he will in all 
probability die in confinement (YH, vol. 1, p. 319, ed. 3). 
Bechstein (BC), an ardent bird-fancier, though he can hardly 
be called a bird-lover, states that the nightingale’s song is 
