I’m not sure if this is a glitch or it’s what really happens but I usually carry one into a wooden taming pen and leave it there for a while. While waiting I go do random things, like kill a bunch of things at Carno Island/The Dead Island for some XP. After around 15-30 minutes I go back and knock it out and give it some Gallimimus Egg Kibble. As soon as I put the kibble in its inventory it tamed immediately. A new way to starve tame I guess? Also there were no corpses or anything in the pen to feed them.
Other people leave old taming traps on the red woods beach. Check then frequently with a argy. The terror birds get stuck in them. If you're careful, you can knock them all out (if its the whole flock) from the edge, then land inside and be safe and cozy for your tame. (Just take plenty of narcs and food)