Something that is very irritating about the argentavis is that after it is over 3/4 torpor, it begins to sprint away, usually upwards. An easy way to combat this is by running after it with a crossbow and/or longneck rifle and to continue pounding it with tranq arrows/darts. Quetzals with platform saddles work well too. Keep a Dino close while chasing them, as argentavises usually spawn where other dangerous creatures spawn, and if you die you will most likely lose your stuff, and more importantly, the argentavis.

More Argentavis Taming & KO Tips