388 THE STRUCTURE AND LIFE OF BIRDS CHAP, 
bottom of streams as he searches for caddis-worms 
or insects, and his breast feathers are dense and 
impervious to water. The Rook may be known 
from the Crow by the absence of feathers on the 
beak; they are worn away through his habit of 
digging in the ground for food. In the young bird 
they are still there, and to make sure whether you 
have a Rook or a Crow you have to look at the 
inside of the mouth; in the Rook, it is deep flesh- 
colour, in the Crow, much paler. 
Though some of these distinctions may appear 
trifling and insignificant, yet it is impossible to study 
classification without learning a great deal that is of 
real interest. There emerges, for instance, the very 
interesting fact that most birds, -which for their size, 
lay large eggs, lay them on the ground, and that 
their young when hatched are covered with down, 
able to run at once or in a few hours, and, before 
long, to fend for themselves. There seems at the 
same time to be another principle at work side 
by side with that just explained—namely, that the 
eggs of a bird which lays a great number must be 
small, in order that she may be able to cover them. 
Certainly many of those whose eggs are largest lay 
only one, or at any rate very few, and their young are 
highly precocious. No infant creature is more inde- 
pendent than the Maleo, a bird about the size of a 
small Turkey, native in the Island of Celebes. The 
mother buries her wonderful egg (weighing 84 to 9} 
ounces—ze., about $th of the weight of a mature 
? See the article on “Eggs” in Newton's Dictionary of 
Birds. 
