134 NATURAL SELECTION > vi 



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 (Nectariniidse). 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 



