Birds Follow a Herd of Water Buffalo to Catch Insects

Birds follow a herd of water buffalo to catch insects that are disturbed as the large herbivores walk through the grass. When large predators are near, the birds fly into the air and make warning calls. Who are the birds warning?

A) The water buffalo's prey, because they need to escape
B) The predators, so they know their prey, the water buffalo, is near
C) The water buffalo, so they can avoid attack
D) Their competitors
E) Other birds, who also catch insects stirred up by the water buffalo