134 
NATURAL SELECTION 
vt 
other surrounding objects, before we can say that the bird, 
when sitting on its nest, is really conspicuous. It has been 
remarked that small patches of white and black blend at a 
short distance to form gray, one of the commonest tints of 
natural objects. 
5. Sunbirds (Ncctariniidse). In these beautiful little birds 
the males only are adorned with brilliant colours, the females 
being quite plain, yet they build covered nests in all the cases 
in which the nidification is known. This is a negative rather 
than a positive exception to the rule, since there may be other 
causes besides the need for protection which prevent the 
female acquiring the gay colours of her mate, and there is one 
curious circumstance which tends to elucidate it. The male 
of Leptocoma zeylanica is said to assist in incubation. It is 
possible, therefore, that the group may originally have used 
open nests, and some change of conditions, leading the male 
bird to sit, may have been followed by the adoption of a domed 
nest. This is, however, the most serious exception I have yet 
found to the general rule. 
6. Superb warblers (Maluridse). The males of these little 
birds are adorned with the most gorgeous colours, while the 
females are very plain, yet they make domed nests. It is to 
be observed, however, that the male plumage is nuptial 
merely, and is retained for a very short time; the rest of 
the year both sexes are plain alike. It is probable, there- 
fore, that the domed nest is for the protection of these 
delicate little birds against the rain, and that there is some 
unknown cause which has led to the development of colour 
in the males only. 
There is one other case which at first sight looks like an 
exception, but which is far from being one in reality, and 
deserves to be mentioned. In the beautiful waxwing (Bom- 
bycilla garrula) the sexes are very nearly alike, and the 
elegant red wax tips to the wing-feathers are nearly, and 
sometimes quite, as conspicuous in the female as in the male. 
Yet it builds an open nest, and a person looking at the bird 
would say it ought, according to my theory, to cover its nest. 
But it is, in reality, as completely protected by its coloration 
as the most plainly coloured bird that flies. It breeds only 
in very high latitudes, and the nest, placed in fir-trees, is 
