38 NATURAL SELECTION in 



snowfields and icebergs. The polar bear is the only bear 

 that is white, and it lives constantly among snow and ice. 

 The arctic fox, the ermine, and the alpine hare change to 

 white in winter only, because in summer white would be 

 more conspicuous than any other colour, and therefore a 

 danger rather than a protection; but the American polar 

 hare, inhabiting regions of almost perpetual snow, is white all 

 the year round. Other animals inhabiting the same Northern 

 regions do not, however, change colour. The sable is a good 

 example, for throughout the severity of a Siberian winter it 

 retains its rich brown fur. But its habits are such that it 

 does not need the protection of colour, for it is said to be able 

 to subsist on fruits and berries in winter, and to be so active 

 upon the trees as to catch small birds among the branches. 

 So also the woodchuck of Canada has a dark-brown fur ; but 

 then it lives in burrows and frequents river banks, catching 

 fish and small animals that live in or near the water. 



Among birds, the ptarmigan is a fine example of protective 

 colouring. Its summer plumage so exactly harmonises with 

 the lichen-coloured stones among which it delights to sit, that 

 a person may walk through a flock of them without seeing a 

 single bird ; while in winter its white plumage is an almost 

 equal protection. The snow-bunting, the jer-falcon, and the 

 snowy owl are also white-coloured birds inhabiting the arctic 

 regions, and there can be little doubt but that their colouring 

 is to some extent protective. 



Nocturnal animals supply us with equally good illustrations. 

 Mice, rats, bats and moles possess the least conspicuous of 

 hues, and must be quite invisible at times when any light 

 colour would be instantly seen. Owls and goatsuckers are of 

 those dark mottled tints that will assimilate with bark and 

 lichen, and thus protect them during the day, and at the 

 same time be inconspicuous in the dusk. 



It is only in the tropics, among forests which never lose 

 their foliage, that we find whole groups of birds whose chief 

 colour is green. The parrots are the most striking example, 

 but we have also a group of green pigeons in the East ; and 

 the barbets, leaf-thrushes, bee-eaters, white-eyes, turacos, and 

 several smaller groups, have so much green in their plumage 

 as to tend greatly to conceal them among the foliage. 



