188 THE STORY OF THE BIRDS. 
While a bird knows geography only in the line of 
its needs or its forefathers’ uses, it may tell us a great 
deal of a condition of the earth that no human eye 
has ever seen. Taking the world over, we can look 
back through the bird’s inherited knowledge and get 
glimpses of ancient geography away beyond our old- 
est records. The entire subject of the distribution of 
birds and other animals is full of such suggestions. 
In connection with what a bird knows we may 
mention its knowledge of numbers. All creatures 
appear to distinguish 
between many and 
few, and all know 
the value or force 
of great numbers. 
Wolves become 
fierce when the pack 
is large, and jays, 
crows, and others are 
valiant in their attack 
on owl and eagle after 
they have called up a crowd. 
But it seems that within 
a small limit birds have a correct, 
A crow. or nearly correct, estimate of the 
number of objects present. This 
is especially noticeable in the behavior of some birds 
with regard to the proper number of eggs that should 
be in the nest before they begin to incubate, or 
rather before they stop laying. Many birds do not 
have a definite number in their clutch, but all have 

