DIPPER 
59 
than a man's head, in some hole or cranny of the 
rocks and boulders of the stream, or the stones of a 
bridge, mill-dam, or neighbouring wall, and some- 
times actually behind the curtain of a falling 
cascade. Often the nest is so like the mossy 
surface of the surrounding stones that it is very 
hard to detect, and it is often hidden deep among 
the crevices of a heap of boulders ; sometimes, 
however, when built beneath a bridge, on the lower 
flange of an iron girder, or some similar situation, 
it is as conspicuous from below as a football placed 
on a shelf. The hole is low down at one side, and 
the nest is generally lined with dry leaves. Five 
or six eggs are laid, somewhat smaller than a 
Starling's, and pure white. The song may be heard 
in autumn, and sometimes in winter, while it begins 
anew very early in the spring, when the birds 
begin to think of nesting. A good instance of the 
difficulty which is often found in deciding what is 
a separate species, as distinct from a mere variety or 
local form, is supplied by the so-called Black- 
bellied Dipper {Cinclus melanogaster)^ which takes 
the place of our particular bird in Norway, Sweden, 
and North Russia, and sometimes wanders to this 
country. It is a matter of scientific dispute, as in 
many similar cases, whether it should really be 
regarded as a distinct species or not, some ornitholo- 
gists wishing to give a separate specific standpoint 
