Thanks for that. It looks like you're fighting a decent bit of underexposure, plus heavy cropping there; to really get the sharp, detailed shots you see here, you need to get your exposure better but even more importantly, you need the bird filling more of the frame to begin with.
It certainly explains some of what we see in the edited shot. When you've got an image that is this underexposed, you have to push that up in post to get to where your edit was, which brings out noise much stronger. For a situation like that one, if you had run your ISO up a stop or so (to 800+) you could have had a much brighter image and pulled it back slightly in post. That would have helped keep your owl more white, and not given that odd green/red coloring in the chest barring that you see in the original.
Also, getting closer is really the trick with any lens. For example, this shot is from our irruption on the West coast, 2 years ago. This is a full height framing at 400mm, crop was rotated to portrait, so it only cropped off the edges. (click through to the actual Flickr post for a sharper version)
Snowy Owl-6983 by
Guideon72, on Flickr
This was the first year they came down and the birds were much more tolerant of people at that point. The next year, they're been pressed hard enough by people including the (juvenile twits I saw chasing one waving their coats) that we were hard-pressed to approach the things very close at all.
This is about a 1/3 crop on both edges, from [I'm guessing] 40ft away or so, again, at 400mm. This guy was perfectly happy with all of the photographers standing at that distance, but if anyone got any closer, he'd move further down the log.
IMAGE LINK: http://www.flickr.com/photos/snydremark/8333217083/ Damon Point Snowy Owl-0927 by
Guideon72, on Flickr
Keep working at it, and don't forget that the quality of the light you're working with is going to have as much or more to do with your final outcome than the quantity of the light does.
