322 A HISTORY OF BIRDS 



proval, they have never identified these birds. Accordingly I 

 wrote, for the purpose of this chapter, to my friend Dr. John- 

 athan Dwight, a distinguished American Ornithologist, asking 

 him for confirmation of this statement, and the names of the 

 Swallows. He replied that he had no knowledge of the fact, 

 and further that he had every reason to believe that Darwin 

 had been misinformed on this matter. The statement con- 

 cerning the Missel-thrush is also not confirmed. 



Among birds which rear two or three broods in a year it is 

 no uncommon thing for the young of the first brood to assist 

 in feeding those of later broods, as for example in the Common 

 Water-hen {Gallinula chloropus) and among the Thrush tribe. 

 On the other hand, birds which have but few young, and a 

 relatively limited food supply, spread over a large area, drive 

 away their young so soon as they are able to fend for them- 

 selves, as for instance among the Eagles and Ravens. Un- 

 natural as this may seem, such conduct when more closely 

 examined proves, on the contrary, to be extremely prudent, 

 since the struggle for existence is lessened thereby, both for the 

 parents and the offspring. Moreover, Eagles do not become 

 mature for many years, so that, during this period of infertility 

 these immature birds would seriously endanger the lives of all 

 the subsequent broods reared by their parents, while, on attain- 

 ing fertility they would still further intensify the struggle for food. 



Striking as are the facts herein set down they are completely 

 eclipsed, in interest, by those which that able naturalist Dr. 

 A. E. Wilson has placed on record with regard to the Antarctic 

 Penguins. And these will be found set forth in some detail in 

 Chapter XVI. 



Protective Coloration 



The several instances so far quoted show selection at work 

 in its most violent fashion — banishing, or exterminating, the 

 weaker. But in Nature might is not always right, and the battle 

 is not always to the strong. The persecuted contrives, not 

 seldom, to escape by subterfuge — sometimes apparently de- 

 liberate, as by feints either of death or injury. In the cases of 

 which we are now to speak, however, Nature has contrived to 

 secure the survival of the otherwise defenceless by a process of 

 selection which has bad the effect of transforming the superficial 



