If you are near a mountain or place of high elevation shooting the quetz so it runs into the direction of a wall or pillar of some kind is ideal. After it hits the wall hover above the bird and block it from flying up. Hop off your bird and begin shooting. I have used this to solo tame lvl 55 quetz a few times.
The fun way is to jump off and grapple to your argie and whistle it to attack and since argies are slow it won’t catch up in time so tranq till it goes out also bring parachutes and consider liking so more people will know
If you drop a quetzal due to knockout, and it lands next to a giga...just know, the quetzal belong to the giga. Now you get to watch your would be quetzal get eaten by a giga. Now you can go home and cry.