owth of a new and complex instinct
actually under the eyes of human observers.

One word as to the general colouring of the parrot group as a whole.
Tropical forestine birds have usually a ground tone of green because
that colour enables them best to escape notice among the monotonous
verdure of equatorial woodland scenery. In the north, to be sure, green
is a very conspicuous colour; but that is only because for half the
year our trees are bare, and even during the other half they lack that
'breadth of tropic shade' which characterises the forests of all hot
countries. Therefore, in temperate climates, the common ground-tone of
birds is brown, to harmonise with the bare boughs and leafless twigs,
the clods of earth and dead turf or stubble. But in the evergreen
tropics green is the right hue for concealment or defence. Therefore
the parrots, the most purely tropical family of birds on earth, are
mostly greenish; and among the smaller and more defenceless sorts, like
the familiar little love-birds, where the need for protection is
greatest, the green of the plumage is almost unbroken. Of the tiny
Pigmy Parrots of New Guinea, for instance, Mr. Bowdler Sharpe says:
'Owing to their small size and the resemblance of their green colouring
to the forests they inhabit, they are not easily seen, and until recent
years were very hard to procure.' And of the green parrot of Jamaica,
Mr. Gosse remarks: 'Often we hear their voices proceeding from a
certain tree, or else have marked the descent of a flock on it; but on
proceeding to the spot, though the eye has not wandered from it, we
cannot discover an individual. We go close to the tree, but all is
silent and still as death. We institute a careful survey of every part
with the eye, to detect the slightest motion, or the form of a bird
among the leaves, but all in vain. We begin to think they have stolen
off unperceived; but on throwing a stone into the tree, a dozen throats
burst forth into a cry, and as many green birds rush forth upon the
wing. Green may thus be regarded as the normal or basal parrot tint,
from which all other colours are special decorative variations.

But fruit-eating and flower-feeding creatures, like butterflies and
humming-birds--seeking their food ever among the bright berries and
brilliant flowers, almost invariably acquire in the long run an
aesthetic taste for pure and varied colouring, and by the aid of sexual
selection this taste stereotypes itself