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 frequently. 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 lies 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 
