Well done David and great light.
Are these typically 600mm? Your copy is really dialled in and sharp.
At 600mm and f/8, I'm surprised at the thin depth of field I get. I am trying to take enough test shots to see if mine is dialed in properly, because I'm not getting much feather detail.
Would you mind sharing your settings of the robin, for example, and how far away you were? Puplicly or in a PM.