Again, it suffers from a lack of IQ and not entirely from the cropping I think. Wing positions aren't the greatest and maybe a bit too much processing. But I just had to try.... Does it work?
Neat incoming pose, I like the "V" shape (wing position works nicely for the incoming pose). I agree the details are lacking, did you need to sharpen the image more aggressively than usual? I could see this with some cropped more left and bottom.
I did take it to PS and do high pass sharpening to it which is "more" than usually required...and capture sharpening was slightly higher than typical. But the major details were all sharp at capture.
I'm not sure if it's the TC, but I don't really think so as it does quite well with other subjects. I'm thinking it's very slight motion blur due to the bird coming directly at me and the short focal distance (12-15ft).