An easy way to tame a pelagornis is a thatch box on a quetz platform with doorframe walls. Fly into the pelagornis then hop off the quetzal as the pelagornis is forced through the doorframes. It cant get out of the doorframes therefore makes for an easy knockout
Ever need lots of raw fish. Easy! Instead of swimming around in the water risking getting attacked by megapiranhas, simply make a saddle for your Pelagornis, Ride it into the water, and it one shots every small fish.