BIRDS AS BROOD-PARASITES 187 
this peculiarity of theirs has already been dwelt upon. Enough 
to say here that the egg of the parasite is introduced into the 
nest of the dupe, and after the necessary incubation by the fond 
fool of a foster-mother the interloper successfully counterfeits the 
heirs, who perish miserably, victims of his superior strength. 
The whole process has been often watched, but the reflective 
naturalist will pause to ask how such a state of things came 
about, and there is not much to satisfy his enquiry. Certain it 
is that some birds, whether by mistake or stupidity, do not un- 
frequently lay their 
eggs in the nests of ; 
others. It is within ¢) Vii y 
a) 
the knowledge of d 
e iis 
; / 
\ eA ~~ ; 
many that Pheasants’ ia 
eggs and Partridges’ 
eggs are often laid in 
the same nest, and it 
is within the know- 
ledge of the writer ( \\ 
that Gulls’ eggs have \\ 
been found in the 
nests of Eider- Ducks, 
and wice versa; that a 
Redstart and a Pied 
Fly-Catcher, or the 
latter and a_ Tit- 
mouse, will lay their Fig. 1132.—Young vier iad tes ee ee 
eggs in the same con- 
venient hole—the forest being rather deficient in such accom- 
modation; that an Owl and a Golden-Eye will resort to the 
same nest-box, set up by a scheming woodsman for his own 
advantage; and that the Starling, which constantly dispossesses 
the Green Woodpecker, sometimes discovers that the rightful 
heir of the domicile has to be brought up by the intruding tenant. 
In all such cases it is not possible to say which species is so 
constituted as to obtain the mastery; but just as it is conceivable 
that in the course of ages that which was driven from its home 
might thrive through the fostering of its young by the invader, 
and thus the abandonment of domestic duties would become a 
direct gain to the evicted householder, so the bird which, through 
