COLORATION AND HABITS OF BIRDS 35 



vertising coloration, are interesting because of their 

 beauty and their habits. They are also interesting 

 because they offer such illuminating examples of the 

 truth that many of the most common and successful 

 birds not merely lack a concealing coloration, but 

 possess a coloration which is in the highest degree 

 revealing. The coloration and the habits of most of 

 these birds are such that every hawk or other foe that 

 can see at all must have its attention attracted to them. 

 Evidently in their cases neither the coloration nor any 

 habit of concealment based on the coloration is a sur- 

 vival factor, and this although they live in a land teeming 

 with bird-eating hawks. Among the higher vertebrates 

 there are many known factors which have influence — 

 some in one set of cases, some in another set of cases — in 

 the development and preservation of species. Courage, 

 intelligence, adaptability, prowess, bodily vigour, speed, 

 alertness, ability to hide, ability to build structures which 

 wiU protect the young while they are helpless, fecundity 

 — all, and many more like them, have their several places ; 

 and behind all these visible causes there are at work other 

 and often more potent causes of which as yet science can 

 say nothing. Some species owe much to a given attri- 

 bute which may be wholly lacking in influence on other 

 species ; and every one of the attributes above enumer- 

 ated is a survival factor in some species, while in others 

 it has no survival value whatever, and in yet others, 

 although of benefit, it is not of sufficient benefit to offset 

 the benefit conferred on foes or rivals by totally different 

 attributes. Intelligence, for instance, is of course a sur- 

 vival factor; but to-day there exist multitudes of animals 

 with very little intelligence which have persisted through 

 immense periods of geologic time either unchanged or 

 else without any change in the direction of increased 



