Cuckoo's nest

is something of a false term, since all Australian cuckoos, with the exception of the Pheasant Coucal which I've mentioned before, lay their eggs in the nests of birds of other species, leaving it to them to rear its offspring. They choose a bird whose eggs are similar to its own—for the big channel-billed cuckoo, it's the nests of crows & currawongs; for the small black-eared cuckoo, speckled warblers & redthroats. In other words, young cuckoos are parasites.

The koel, according to my bird book, "lays her marbled salmon-pink egg or eggs in the nest of one of a number of hosts such as friarbirds or other large honeyeaters." Which explains why, this morning, in a tree in the front yard, a young koel, fresh from the nest, was angrily screeching for its pressganged "parents"—in this case, a pair of blue-faced honeyeaters smaller than it—to bring it food. & they were complying, over & over.

What I don't understand is why the cuckoo-raisers don't just abandon the fledgling when it becomes apparent that it isn't theirs. It strikes me as if some sort of bizarre imprinting-in-reverse is also at work. I'm guessing that there were/are other, genuine, offspring; what happens to them whilst Mum & Dad are out spending the major part of their lives attempting—not too successfully, judging by the screeching—to assuage the hunger of this space invader?

Couldn't find the camera to capture the scene, but I did find the photo below, of a similar occurence, at debra21's photosteam on Flickr.