For an easy tame, wait for the Lymantria to land and then place a tent directly where he/she is at. Its stuck until the tents durability dies out, this gives you enough to build a little house around it for a safe, easy tame.
Don't attack it unless u have a plan a good one is to wait for it to land, throw a normal bola at it, then shoot tranq arrows at its head until it passes out, then feed it mejoberries or any type of berries, you may want to build a house around it to protect you and the lymantria from storms
A lymantria can fit through a single ceiling tile space but an argentavis can't. Build a trap with one ceiling missing in the corner. Use a lymantria to aggro an argentavis, fly into the trap and out the hole, leaving the argentavis in the trap. Easy argentavis tame.
The way I knocked my first one (don't tame when the raptor rockdracke guys are close) is with a bola and a club they eat berry but they cannot collect, There only Attack is a spore type attack, they slow down who, or whatever is in its radius...
I would highly recommend building some sort of trap when taming a high level. Otherwise, without a good tier weapon, even a bola won't prevent a high level from breaking free and flying off before you knocked it out! ~L