An eagle's talons are incredibly sharp and the have a high pound per square inch crushing pressure (maybe 200 pounds per square inch). An eagle could easily grab an ostrich by the head or neck and kill it. read more
Looking at the armour of the eagle it is very much possible for the eagle to kill the ostrich. But the trade off in this wouldn't really favour the eagle since the investment from eagle’s side will be tremendous when it comes to an ostrich. read more
Also, any bird that can carry a rock big enough and high enough then drop it on a human's head could kill a human (hawks, eagles, vultures, etc.) or any bird with enough body weigh to knock a person over and peck/scratch (emu, ostrich, etc.) or a flock of flight-full birds could kamikaze with a human. read more