When I went out I consciously decided to use the wider primes on the 7D, and specifically not go ducking or birding in general. You can guess what happened... they all came out laughing at my lens choice. Robins were singing less than 2m away, similar distances for crows and even the paranoid magpies didn't fly away. To top it off, I saw my first wild rabbits of the year. One didn't run from me, and a 400mm would have been ideal to get a tight shot.
The longest lens I had with me was the Sigma 150mm macro, with 1.4x TC giving 210mm. On critical inspection, it is front focusing enough to be a problem. Even when the focus is on, it is not sharp wide open. Trying to set the AF micro-adjust in the field probably wasn't the best way to do it either, and in the end worked around by stopping down and compensating by jacking up the ISO even in direct sunlight.
There's always next time I guess... pics to follow in the usual threads.
_________________Canon DSLRs: 7D2, 7D1, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 10-18, 15-85
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 50/1.4A, 150 macro, 120-300 f/2.8 OS
Compacts: Sony HX9V, Fuji X100.