256 4 THEORY OF BIRDS NESTS. 
hues of the head and back, together with the yellow 
of the wings and tail, are tints that exactly harmonize 
with the colours of various species of lichens, while 
the brilliant red wax tips exactly represent the crimson 
fructification of the common lichen, Cladonia cocci- | 
fera. When sitting on its nest, therefore, the female 
bird will exhibit no colours that are not common 
to the materials of which it is constructed; and the 
several tints are distributed in about the same pro- 
portions as they occur in nature. At a short distance 
the bird would be indistinguishable from the nest it is 
sitting on, or from a natural clump of lichens, and 
will thus be completely protected. 
I think I have now noticed all exceptions of any 
importance to the law of dependence of sexual colour 
on nidification. It will be seen that they are very 
few in number, compared with those which support 
the generalization; and in several cases there are 
circumstances in the habits or structure of the species 
that sufficiently explain them. It is remarkable also 
that I have found scarcely any positive exceptions, 
that is, cases of very brilliant or conspicuous female 
birds in which the nest was not concealed. Much less 
can there be shown any group of birds, in which the 
females are all of decidedly conspicuous colours on 
the upper surface, and yet sit in open nests. The 
many cases in which birds of dull colours in both 
sexes make domed or concealed nests, do not, of course, 
affect this theory one way or the other; since its 
purpose is only to account for the fact, that brilliant 
