2 - 3 Tranq arrows will successfully knock out an argentavis. Then, I gave the bird several pieces of meat and several types of berries. I left it and did other tasks. Came back a while later and it was tamed. I've done this 3 times successfully.
To tame one easy all you have to do is kill something so the argent Avis can eat, and while it’s healing you must knock it out with tranq arrows or darts. If it is knocked out while healing it’ll starve immediately and it’ll tame in seconds no matter what level!
If you lose your argys go to the place that shows your character press the tames button which says how much animals you have, Look for your argys name press request, then wait. It will tp to you, if it’s alive.