272 FIELD ZOOLOGY. 



It is a fact that will probably hold good throughout the 

 animal kingdom that organisms of high nervous organ- 

 ization are more open to variation in any of its modes 

 of approach. These climatically produced subspecies are 

 to be regarded as variations upon a single species ; but if 

 the climatic barriers were destroyed, or if some climatic 

 revolution were to cut off the intervening species completely 

 from each other, .then, in the first supposed case, the 

 subspecies would gradually disappear, all the individuals 

 tending toward one form, expressing the fact that climate 

 had the same measure of effect upon all ; or, in the second 

 supposed case, the subspecies would, in time, appear as 

 distinct species, each having its own definite, persistent, 

 unvarying characteristics. 



The matter of the bird's individual plumage seems 

 to have definite relation to its environment and its plan of 

 food-getting. Colors of plumage seem to be deceptive, 

 protective, and attractive. Birds spending the life 

 round in one region, frequently have a winter and a summer 

 plumage. The ptarmigan in its winter home on the 

 mountain slopes is snowy white, and in summer, brown- 

 mottled. This is protective coloration. But the snowy 

 owl, which lives in about the same regions, is snow-white 

 in winter also ; and often makes a meal off the ptarmigan 

 because of this fact. This is deceptive coloration. 

 Fruit-eating birds are often brilliantly colored to keep 

 you from seeing what they are doing. Not that they 

 know that you like fruit better than they do, or are 

 better entitled to it (either fact need not be conceded), 

 but as animal against animal in the struggle for getting 

 enough to eat, when they are best nourished by fruit, 

 they are best assured of getting enough of it by being 

 fruit-colored. 



