What do you need 10 bits for? Advanced color correction?
Not for publishing, as all intenet / television delivery is 8 bits, and you have to be lucky if your end user has an 8 bit capable monitor. The theatre is 12 bit, but there is no single one on this site who solely produces for the theatre. And if you do, you should be able to afford a normal cam.
As you stated yourself, the Sony is highly seniitve, so you should be able to do proper exposure untill dark.
(Ok, hard to shoot owls.)
Now, if your shot is not steady, you have to trash it.
If your shot is out of focus, you have to trash it. (I know birds, they tend to fly around a lot, hard to keep focus.)
So, anything that makes focus / stabilization easy is of utmost importancy.
For editing, give me 10 decent exposed / stabilized shots over 10.000 bad ones any day. The end result with just 10 good shots WILL be better.
So, pick your poison.
Or, go work at the local factory for a couple of weeks and get an FS-7.
Bouke
http://www.videotoolshed.com