[Chip]

I use a borrowed 70-300mm for bird photography, too - isn't it amazing how inadequate 300mm can be at time??

For this shot, given that the bird was in the shade and the sky is so bright, I think you did well. The bird, though, still seems just a bit underexposed. Could you possibly lighten the whole photo just a bit, or maybe even select the owl and lighten just that?

And this comment is one based on personal taste, but I tend to not bump up the saturation much at all for wildlife photos. So, to me, the saturation here is a little too much.

Good work. Photographing birds in mixed light isn't easy.

Now, you just need to save up and buy a fast 400 mm prime!