It is not really about criticising the lens, I think it is a great lens, the question is, is it working right?
You didn't confirm whether you were using a filter? If you are, then take the filter OFF.
From the the images you posted, the lens might need some callibration.
One other point, 1/320 is not nearly fast enough shutter speed for birding. The minimum is 1/500 and the f-stop should be at least f/5.6.
How old is the lens? If this was my lens, I would return it and get another 100-400L. The 100-400L is one of the Canon lenses I would not buy used along with the 50L.