Chap. XIII. 
INSTRUMENTAL MUSIC. 
61 
from a distance to a male under confinement; but as 
the black-cock continues his sjpel for hours during 
successive days, and in the case of the capercailzie 
^^with an agony of passion,” we are led to suppose 
that the females which are already present are thus 
charmed.^^ The voice of the common rook is known 
to alter during the breeding-season, and is therefore in 
some way sexual.^® But what shall we say about the 
harsh screams of, for instance, some kinds of macaws ; 
have these birds as bad taste for musical sounds as 
they apparently have for colour, judging by the in- 
harmonious contrast of their bright yellow and blue 
plumage? It is indeed possible that the loud voices 
of many male birds may be the result, without any 
advantage being thus gained, of the inherited effects of 
the continued use of their vocal organs, when they are 
excited by the strong passions of love, jealousy, and 
rage ; but to this point we shall recur when we treat of 
quadrupeds. 
We have as yet spoken only of the voice, but the 
males of various birds practise, during their courtship, 
what may be called instrumental music. Peacocks 
and Birds of Paradise rattle their quills together, 
and the vibratory movement apparently serves merely 
to make a noise, for it can hardly add to the beauty 
of their jilumage. Turkey-cocks scrape their wings 
against the ground, and some kinds of grouse thus 
produce a buzzing sound. Another North American 
grouse, the Tetrao umbellus, when with his tail erect, 
his ruffs displayed, ^^he shows off his finery to the 
females, who lie hid in the neighbourhood,” drums 
tapidly with his lowered wings on the trunk of a 
L. Lloyd, ‘The Game Birds of Sweden/ &c., 1867, p. 22, 81. 
Jenner, ‘ Philosoph. Transactions,’ 1824, p. 20. 
