6 Evolution and Adaptation 
white coat in winter, and a brown coat in summer. The 
white winter plumage renders the animal less conspicuous 
against the background of snow, while in summer the 
plumage is said to closely resemble the lichen-covered 
ground on which the bird rests. The snowy owl is a north- 
ern bird, whose color is supposed to make it less conspicuous, 
and may serve either as a protection against enemies, or 
may allow the owl to approach its prey unseen. It should 
not pass unnoticed, however, that there are white birds in 
other parts of the world, where their white color cannot be 
of any use to them as a protection. The white cockatoos,.... 
for example, are tropical birds, living amongst green foliage, 
where their color must make them conspicuous, rather than 
the reverse. 
The polar bear is the only member of the family that is 
white, and while this can scarcely be said to protect it from 
enemies, because it is improbable that it has anything to fear 
from the other animals of the ice-fields, yet it may be claimed 
that the color is an adaptation to allow the animal to ap- 
proach unseen its prey. 
In the desert many animals are sand-colored, as seen for 
instance in the tawny color of the lion, the giraffe, the 
antelopes, and of many birds that live on or near the ground, 
It has been pointed out that in the tropics and temperate 
zones there are many greenish and yellowish birds whose 
colors harmonize with the green and yellow of the trees 
amongst which they live; but on the other hand we must 
not forget that in all climes there are numbers of birds 
brilliantly colored, and many of these do not appear to be 
protected in any special way. The tanagers, humming-birds, 
parrots, Chinese pheasants, birds of paradise, etc., are ex- 
tremely conspicuous, and so far as we can see they must "°° ° 
be much exposed on account of the color of their plumage. 
Whether, therefore, we are justified in picking out certain 
cases as examples of adaptation, because of an agreement in 
