The Descent of Man

is clear, for a sterile, hybrid canary-bird has
been described (31. Mr. Bold, 'Zoologist,' 1843-
44, p. 659.) as singing whilst viewing itself in a
mirror, and then dashing at its own image; it
likewise attacked with fury a female canary,
when put into the same cage. The jealousy excited
by the act of singing is constantly taken
advantage of by bird-catchers; a male, in good
song, is hidden and protected, whilst a stuffed
bird, surrounded by limed twigs, is exposed to
view. In this manner, as Mr. Weir informs me, a
man has in the course of a single day caught
fifty, and in one instance, seventy, male chaffinches.
The power and inclination to sing differ
so greatly with birds that although the price
of an ordinary male chaffinch is only sixpence,
Mr. Weir saw one bird for which the birdcatcher
asked three pounds; the test of a really
good singer being that it will continue to sing
whilst the cage is swung round the owner's
head.