It is possible to insert it in the trachea. This is why I always feel for the tube in the esophagus before giving fluids or food.
I go until the tube bottoms out in the crop, then back up a little.
If you can feel the tube in the crop you know it's in the right place. Hard to go "too far"...
With the chickens, ducks, and peafowl I sit on the sofa with my thighs parallel to the ground. I place them in my lap with their feet on my left thigh and press them down and and against my torso with my left arm. Then with them pressed against my body I take my left hand, extend their neck...