If you don't have another Quetzal, the easiest way to tame it is to use Argentavis - Grappling hook strategy. Set up keys for attack this target and move to in settings. Then jump from Argentavis and hook onto him (do this at low altitude in case you fall). Then you just whistle move to Quetzal and shoot with Tranquilizer Darts from Longneck Rifle. When it starts fleeing whistle attack on Quetzal so that you catch up with him. Make sure that you whistle move to before Argentavis actually attacks Quetzal. Super spyglass is of great help too because you can see torpidity and make sure you don't knock it out above water