Heres a few tips about the argentavis:

1-If they eat any corpse, they will start rapidly gaining health.

2-They have a 50% weight reducement(is that a word lol) on metal ore, crystal or obsidian.

3-They can carry medium sized creatures, like an anky, raptor, or parasaur.

4-You can use these guys to farm metal with an anky, grab an anky with the argy and bring it to a location with lots of metal and start farming that metal with your anky.

-Pablo :D