On looking carefully you can see that this bird has a chick in its bill as it jumps from the nest. What I don't know is whether it is a dead Square-tailed Kite chick or merely food that the Kite was bringing for its chicks.
Either way the chick was obviously dead. The kite sat on a nearby branch and pecked away at the dead chick for a while and then jumped back into the nest. Maybe it was just tenderising food for its own chicks.