It was reaching dusk when I added the 1.4x teleconverter resulting in 1120mm.
This night heron had no direct light, so ISO 1600 and 1/100 shutter speed were needed.
I'm very pleased with the results considering the conditions and slow shutter speed.

Taken during my first outing with new Sigmonster lens and 1D Mark III camera.
More images taken with this lens can be seen here.