Two Pied-billed male Grebes attacking an Eared Greebe.

I've never seen this behavior before. Appeared the Pied-bill was trying to kill the Eared. It had its beak around the neck and took it underwater several times. The Eared got away once and they chased it down and went at it again. Eventually, the Eared got away and flew over to the shore of the pond, and the two Pied-bills gave up and swam away.