Last weekend I micro-adjusted my 300/2.8 and 2X extender to the 1D4 body and took them for a spin on my most recent visit to the Centennial Park in Sydney.
This fella was funny to shoot.
But the most fun and rather amazing was shooting at ISO 12800.
I couldn't do it with my 1Ds3, no way ... Very happy.
-mirek
Enjoy the bird with an attitude at high ISO with 1D4.