These were taken on Sunday on my way to Denver, from a roadside rest area looking into the next-door corn field. The birds were pretty cooperative, allowing me to get right up to the fence line with camera and tripod without spooking. They were only about 20 yards away... K100D with Promaster 70-300 stacked on a Zykkor 2x TC, shot in M mode since the (old) TC made it manual anyway...
Image quality wasn't too bad, considering the narrow DOF at 600mm and the fact I was using the factory viewfinder/focus screen. I did have to tweak the levels on a couple of the photos to compensate for the TC. Sharpness adjustments were no more than I normally would do on lesser lens length, I am pretty happy with these.
I think I like the second image most, because of the visible horizon, but the third is also nice, it has the best separation of the cranes from the background!