D300 400 f/2.8 VR tc20E III
Alot of folks don't like this tc, but I think these two shots show decent feather detail. They were taken @f/8 however,VR on, and processed in NX2 from .nefs with some USM. I think this combo works rather well, but you need lots of sunlight.

1. Kingbird


2. Killdeer