|Male Greater Honeyguide, Tarangire NP, August 2011|
Here are some particularly gruesome images of what happens inside a nest parasitised by Greater Honeyguides. In it you'll see how the chick, hatched about 3 days earlier than the hosts (in this case bee-eaters nesting in a termite mound) has already grown rather large and has a massive and nastily hooked beak with which it quickly and efficiently slaughters the hatching bee-eaters, one after the other. Very mean.
There accompanying text says more than enough for me to just point you there to look at – massively high parasitism rates, but most of those parasitised nests are immediately abandoned; female honeyguide tried to stab the host eggs when she lays hers, but the chick is perfectly capable of killing off the competition (even in pitch black, remember!), etc., etc. Nasty business, brood parasitism... Obviously fairly successful though, given the number of groups that practice it here in Africa – cuckoos, honeyguides, whydahs, etc. It must have evolved several times. Anyway, you can get all the details over here, and the original research is published here.