The Descent of Man

male of our common blue tomtit (Parus caeruleus),
is "much less brightly coloured" than the
male: and in the magnificent Sultan yellow tit
of India the difference is greater. (24. Macgillivray's
'British Birds,' vol. ii. p. 433. Jerdon, 'Birds
of India,' vol. ii. p. 282.)
Again, in the great group of the woodpeckers
(25. All the following facts are taken from M.
Malherbe's magnificent 'Monographie des Picidees,'
1861.), the sexes are generally nearly alike,
but in the Megapicus validus all those parts
of the head, neck, and breast, which are crimson
in the male are pale brown in the female.
As in several woodpeckers the head of the male
is bright crimson, whilst that of the female is
plain, it occurred to me that this colour might
possibly make the female dangerously conspicuous,
whenever she put her head out of the
hole containing her nest, and consequently that
this colour, in accordance with Mr. Wallace's
belief, had been eliminated. This view is