I normally shoot with the 1D MkIIN which is a x1.3 crop sensor. If I want more magnification I switch to a 20D body which has a x1.6 crop sensor. Doing this means I effectively get the effect of a TC without having to use one. But sometimes I need the focussing speed of the 1D so I use the TC
Looks like a battering ram, haha! I like the way the body tapers back to the tail feathers, and I like the position of the wings in this shot. I like the blur of the background, too, puts all the focus onto the owl, and he certainly looks magnificent. Nice shot.
I don't know what lens you used but even if it was 600/4 with some TC you must have been pretty close to them - even with car it's for me really incredible! although some days ago I've met hawk owl and pigmy owl - I could walk to them very close ( not enough for good shots though :/ ).
Anyway - great job and great photos!