聚焦速度跟镜头关系大还是跟相机关系大？ Both are important, your 6D should be very good,not as fastas 5DIII or 1Dx.
打飞行中的鸟是不是要放到stablizer mode 2上面？ Mode 2 is panning mode, in my experience, to shoot bird in fly, you need fast shutter speed, 1/1500 or faster, stablizer is not very useful in this speed (for slower speed, it is very important). Use Al servo mode.
1.8m-∞不是已经包含了6.5-∞？Yes.
Use tripod,cable release (or use self timer), test multiple focal length,aperture, make sure your photos are in focus and sharp, good color.
If you have another good lens, use that as a reference.
