That is taken at 185mm on a canon 75-300.. Not nearly as sharp between 200 and 300mm.. Not every day you get a chance of being this close to the birds!
Nice images, The Cormorant and Duck look pretty sharp. But your right, your lens get really soft at longer lengths. I do like the Oystercatcher also...
These are suberb! I love your cormoran, sharp close-up
#2 and #4 have beautiful composition.
in the duck picture, I love the colors in the water, and the expression.