140 Evolution and Adaptation 
imately infer is, that, although the normal instinct has been 
changed into another, the race has still been able to remain 
in existence. The same conclusion applies to the case of 
Molothrus bonariensis, cited by Darwin, and is here even more 
obvious : — 
“Some species of Molothrus, a widely distinct genus of 
American birds, allied to our starlings, have parasitic habits 
like those of the cuckoo; and the species present an interest- 
ing gradation in the perfection of their instincts. The sexes 
of Molothrus badius are stated by an excellent observer, Mr. 
- Hudson, sometimes to live promiscuously together in flocks, 
and sometimes to pair. They either build a nest of their own, 
or seize on one belonging to some other bird, occasionally 
throwing out the nestlings of the stranger. They either lay 
their eggs in the nest thus appropriated, or oddly enough 
build one for themselves on the top of it. They usually sit 
on their own eggs and rear their own young; but Mr. Hudson 
says it is probable that they are occasionally parasitic, for he 
has seen the young of this species following old birds of a 
distinct kind and clamoring to be fed by them. The parasitic 
habits of another species of Molothrus, the JZ donariensis, 
are much more highly developed than those of the last, but 
are still far from perfect. This bird, as far as is known, 
invariably lays its eggs in the nest of strangers; but it is 
remarkable that several together sometimes commence to 
build an irregular untidy nest of their own, placed in singu- 
larly ill-adapted situations, as on the leaves of a large thistle. 
They never, however, as far as Mr. Hudson has ascertained, 
complete a nest for themselves. They often lay so many eggs 
— from fifteen to twenty —in the same foster-nest, that few 
or none can possibly be hatched. They have, moreover, the 
extraordinary habit of pecking holes in the eggs, whether of 
their own species or of their foster-parents, which they find 
in the appropriated nests. They drop also many eggs on the 
bare ground, which are thus wasted.” 
