I've since done a little research on this and now have a somewhat clearer understanding of brood parasites and I've learned that it's no simple matter. However, one thing is apparent and that's despite there being many quite logical theories about it there's no clear proof about why the parasites and those being parasitized act the way they do—see my comment to vagrantJin.
That's ingesting to know. What about the black currawong (they're the only species I've experience of)?
You may also wish to answer the question I've asked elsewhere, which is the cuckoo's inate behavior must also extend to the species it selects as surrogate hosts for its young (would it risk laying an egg in an eagle's nest at the risk of becoming food?).
I've since done a little research on this and now have a somewhat clearer understanding of brood parasites and I've learned that it's no simple matter. However, one thing is apparent and that's despite there being many quite logical theories about it there's no clear proof about why the parasites and those being parasitized act the way they do—see my comment to vagrantJin.