Just a few shots hand held at 600mm. Some at 1/40th. Second. The Cormorant taking off was rather a long way off. Hand held at 600mm. and enlarged to 5 times size. All have been printed at A3 and on canvas.
I have the Sigma 150 - 600 (non sport) and love it. Definitely too heavy to hand hold and you will need a heavy duty tripod and head for it. I actually use a gimball head when using that lens. It adds more stability. Also recommend a remote or cable shutter release.