My problem with wildlife has more to do with operator headspace and timing. For instance, I had been taking some wide-angle shots from near the top of Mt. Pinos using an M 24mm 2.8 lens. A Stellars Jay landed on a branch not that far from me - the blue was almost irridescent the way the sun was shining on it. I quickly switched to the A*300 and got off several quick shots before it flew off. When I reviewed them I realized I had the camera still on M mode and the aperture/shutter speed combination overexposed the shots beyond redemption. That's one of the reasons I find it hard to leave one of the cameras at home when I'm out hiking.
I had exactly the reverse. I was hunting subject with my 300mm and all of a sudden I sensed a couple of woodpeckers were hungry and ready to come to me for food. Very lucky I had my fisheye on another DL and had these lucky shotsin series
My sling bag AW200 really helped.