8 
Bird-Song : and Neu) Zealand Song Birds 
Thus of the harmonics heard easily by the average ear, the 
fifth only differs appreciably, and that by only five vibrations. 
It must be observed, however, that a keen ear may detect a 
difference of one vibration in a thousand; and violin players of 
good ear are inclined naturally to play the natural and not the 
tempered notes. In the natural notes G sharp, say, is slightly 
lower than A flat; in the tempered notes G sharp and A flat 
are the same, occupying a position midway between G and A. 
When birds 7 songs are recorded by means of a keyed pipe, 
certain of the notes appear very slightly sharp or flat; they are 
no doubt the natural notes that are sounded. I have used a 
pipe in either F or G, and no songs have been recorded in keys 
far removed from these two; as, whilst they may have been 
heard, my ear is not keen enough to record more than a short 
song without the aid of the pipe. 
As regards the nature of a bird’s song, I cannot, after long 
observation, agree that it is altogether, or even largely a 
sexual character. Assuming it to be a secondary sexual 
character, many facts can be brought forward in support of the 
assumption. Regarded from another point of view, however, 
bird-song may be seen as a characteristic quite apart from sex, 
but upon which on occasion sex seizes for its own end; and many 
equally cogent facts can be brought forward in support of this 
^ lew. Many emotional elements mingle at the source of song, be 
it bird-song or human song, the sex-emotion being but one. Song 
is a flow ering of the emotions, as speech is a flowering of the 
thought. 
Mudie (MF, vol. 1 , p. 273 et seq . ) notes “the connection be¬ 
tween^ the song and the plumage, and the silence and the 
moult”; and remarks that it “shows that the whole bird is 
subject to some general law, which, though it lies deep beyond 
the power of our divination, governs even the minutest circum¬ 
stance—-the production of a new spot or gloss on a feather, the 
reddening of a comb or a wattle, or the inspiration of courage 
into birds naturally timid. The birds, in fact, blossom in 
spring as well as the plants, and when the purpose of nature 
is accomplished the bloom of the one is shed as well as that of 
