GENERAL DISTRIBUTION. 
169 
be it large or small, settled or unsettled, it becomes 
evident to us that an accurate observer of a bird whose 
geographical range is extensive will find differences 
in the conditions of existence within this range which 
might be easily regarded by an ordinary observer as 
the result of accident, or possibly be over-looked alto¬ 
gether. Thus, my father, a man whose whole life 
had been devoted to the most careful observation of 
birds and their habits, could at once distinguish, among 
other things, the Pied Woodpecker of the fir forest from 
one of another locality. I have been so often convinced 
of the accuracy of his habits of observation, when I have 
questioned the possibility of a suitable basis for similar 
assertions, that I can vouch for the truth of them. 
The land bird is bound to its home by powerful 
bonds which, for the most part, are invisible to our dull 
vision; with some species these limits may perhaps 
embrace an area less than the hundredth part of a mile. 
A large garden and a few trees suffice to form the stage 
upon which a pair of Tree Creepers or Tomtits will act 
their share of life’s work. It is different on the water : 
one wave is like another, their temperature is almost the 
same, their charms are equal, and the bird is cradled 
from one to the other. Unless there is something 
definite or fixed which binds the bird to the spot, it may 
carelessly and unconsciously drift hundreds of miles on 
the broad ocean. In this way we may account for the 
wide distribution of many species of aquatic birds. 
There are limits, however, to the apparently boundless 
ocean as well as to the land. From close observation of 
bird-life, even within a circumscribed area, we are struck 
by the diversity of it, especially with regard to distribu¬ 
tion. The greater or less dependence of bird-life upon 
