Can you post some pics of your Pekins? My female Muscovy's get into cat fights but my Runners and Buff females do not so not sure if this is your 2 females or possibly 2 drakes. Or 3. Yikes don't want to scare you. Hop on top means when one duck will climb on top of another like they are going to mate it can be 2 females or a drake and a female or 2 drakes. They can all do this.