three yellow-billed oxpeckers eagerly pecking on hippo's head in mud, hippopotamus moving, birds taking flight

oxpecker hippopotamus hippopotamus amphibius hippo wildlife conservation southern africa peck pachyderm zimbabwe birds yellowbilled tanzania zambia ear mammal herbivore fauna africa symbiosis protection big mud dangerous closeup environment parasite africanus wild pinworm buphagus unspoiled fearless nature safari wilderness frighten massive maggot lazy movenment eye water outdoors