314 The Bird 



Families of birds; but white blackbirds and such freaks 

 of Nature have but slight chance for life when keen-eyed 

 hawks are ever on the lookout, and owls are alert for 

 every tell-tale plume. Again and again hawks have been 

 known to single out white or whitish birds from a number, 

 making them the object of attack. When any species 

 of bird, through change of habit, absence of enemies, or 

 any other cause, is able to increase greatly in numbers, 

 albinism is likely to occur more frequenth'. A good ex- 

 ample of this is to be found in the naturalized English 

 Sparrows of our cities and towns, among which a remark- 

 able number with white feathers, or even with the entire 

 wings and tail white, are to be seen. This is one of 

 Nature's remedies to reduce the excess number, all need 

 for protective colours having disappeared in the new 

 environment of these birds. We may be certain that if, 

 by any fortunate means, hawks or shrikes can be in- 

 duced to live within the limits of the cities, the albinistic 

 individuals will be the first to fall victims. 



Black phases of plumage occur among some birds, 

 and a double colour-scheme is found in the common 

 Screech Owl, — red and gray individuals being often found 

 in the same brood, the two phases existing independently 

 of age, sex, or season. 



A vast field for future study and investigation hes in 

 the meanings of the differences in colour between the 

 sexes, and in the young birds from both. A hint of the 

 value of ultimate results in this field (which is without 

 the scope of this book) is to be found in our young Ameri- 

 can Robin, whose lower parts, from throat to flanks, are 



