444 The Bird 
species is exposed. I believe that this factor is fairly 
constant for species or tribes of similar habits, and that 
exceptions indicate peculiarities of circumstances which 
in many cases we can easily perceive, because I believe 
that Nature is strictly economical of energy, allowing 
no more eggs to be laid, and consequently young to be 
produced, than the conditions justify in each case. Thus 
the uniformity of avine population—the balance of bird- 
life—is maintained.” 
When a bird’s nest and eggs are destroyed, she will 
often lay another setting, and some birds raise two and 
even three broods in a season under normal conditions. 
If the eggs of a bird are removed as fast as they are laid, 
the bird will sometimes continue to lay, one of the most 
remarkable instances of this in an uncaged bird being 
a Flicker which laid seventy-one eggs during the space 
of three-and-seventy days. <A tiny African Waxbill in 
captivity has been known to rear fifty-four young in the 
course of a year, during the same period laying an addi- 
tional sixty-seven eggs! The domestic hen has become 
a veritable egg-laying machine, thanks to careful breed- 
ing in the past, since the wild Red Jungle Fowl from which 
all varieties of poultry are descended, lays only one nestful 
of seven to twelve eggs once a year. 
Many birds still hold to the old style of nesting in 
hollow trees and such concealed places. Whether they 
hunt around until they find a cavity ready-made by the 
elements, or whether, like the woodpeckers, they pro- 
ceed to excavate a home in a dead branch, or, kingfisher- 
like, to tunnel deep into a sand-bank, their eggs are almost 
