240 4 THEORY OF BIRDS’ NESTS. 
quet, Macaw and Tit, in almost every case as gay and 
brilliant as the male, while the gorgeous Chatterers, 
Manakins, Tanagers, and Birds of Paradise, as well as 
our own Blackbird, have mates so dull and incon- 
spicuous that they can hardly be recognised as be- 
longing to the same species. 
The Law which connects the Colours of Female Birds 
with the mode of Nidification. 
The above-stated anomaly can, however, now be ex- 
plained by the influence of the mode of nidification, 
since I find that, with but very few exceptions, it is 
the rule—that when both sexes are of strikingly gay and 
conspicuous colours, the nest is of the first class, or 
such as to conceal the sitting bird; while, whenever there 
is a striking contrast of colours, the male being gay and 
conspicuous, the female dull and obscure, the nest is open 
and the sitting bird exposed to view. I will now pro- 
ceed to indicate the chief facts that support this state- 
ment, and will afterwards explain the manner in which 
I conceive the relation has been brought about. 
We will first consider those groups of birds in which 
the female is gaily or at least conspicuously coloured, 
and is in most cases exactly like the male. 
1. Kingfishers (Alcedinide). In some of the most 
brilliant species of this family the female exactly re- 
sembles the male; in others there is a sexual difference, 
but it rarely tends to make the female less conspicuous. 
In some, the female has a band across the breast, which 
is wanting in the male, as in the beautiful Halcyon 
