Oh...what is a "history brush"?
In CS2, I use NeatImage on these noisy shots, and do the whole image, bird and all. But it generally smears feather detail so much it's not worth it. To bring the bird back to the original sharpness, I use the history brush on just the bird. The history brush returns whatever it runs over back to the original, or to what layer you select. Now the bird is back to origianl but the background looks smooth. In this case, it was a last ditch effort to save the image enough so you can at least tell what the bird looks like. I had never seen one before, so now I know one when I see another and hopefully others will too. 

