244 WAGTAILS AND PIPITS 



hooded crows), has, for others, to be rationally accounted for. As 

 a matter of fact, I believe, it will be found that Darwin's theory of 

 the origin of the parasitic instinct rests upon quite as or even a 

 more speculative basis than what is here submitted. Needless to 

 say, the class of censors whose wrath is here deprecated, are not 

 quite impartial in their tirades, but in animadverting on the weak- 

 nesses of others, show great human weakness themselves. With 

 them a name is of much more weight than a fact, and their estimate 

 of evidence is in accordance with what they understand to be the 

 official view of the thing about which one is arguing. 1 



I believe that reason has had hardly anything to do with the 

 growth of the parasitic instinct. A bird must build its nest some- 

 where, and what more is it to select the cavity of an old one, for its 

 site, than any other cavity or depression than any other place, in 

 fact, no more, if no less, convenient? To suppose that it says to 

 itself: "Here is a nest almost finished, which I need only have the 

 trouble of lining," is, to my mind, unnecessary. Nest-building with 

 a bird is not the laborious, or, at any rate, not the tedious thing that 

 seems to be commonly supposed, but an instinct, pleasurable in 

 proportion to its strength, and so strong that it is constantly followed 

 beyond the necessary point or period for this I believe to be the 

 real origin of supernumerary nests. 2 Consequently, the idea of saving 

 itself trouble would never have occurred to the bird mind, filled, as 

 it is, with the strong, sweet compulsion of making a nest. But why 

 then is not the old nest, when it has been chosen as a site, speedily 

 buried under another, instead of being, as is sometimes reported, 

 only lined ? The reason may be that no sooner has the bird begun 

 to build, under such circumstances, than the existing nest beneath it 

 becomes confused in its mind with its own work, and after a feeling 



1 See the editorial addition to the footnote on p. 198. 



2 That, and the hen not always being ready to lay her eggs when the nest is finished, as 

 may be assumed from the fact of her not doing so. It is the need of laying, probably, and the 

 instinct of incubation thence arising, that puts a stop to, or checks, that of nidification. 

 Without this, why should we even expect it to end abruptly ? We only do so, because, with all 

 our advanced talk, we are always putting ourselves inside birds. 



