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.

A third species, the M.pecoris of North America, has acquired instincts as perfect as those of the cuckoo, for it never lays more than one egg in a foster-nest, so that the young bird is securely reared.

Mr.
Hudson is a strong disbeliever in evolution, but he appears to have been so much struck by the imperfect instincts of the Molothrus bonariensis that he quotes my words, and asks, "Must we consider these habits, not as especially endowed or created instincts, but as small consequences of one general law, namely, transition ?" Various birds, as has already been remarked, occasionally lay their eggs in the nests of other birds.