Hi Jim - I certainly wouldn't trash it. Perfect exposure and detail. That jagged edge appearence is simply that we are starting to see the barred plumage of the tail. I dont think this is a contest winnter with the flat sky background but I would never trash a shot like this - it's very nice in a more subtle way.
It works for me because of the interesting pose and eye contact. Maybe a bit more contrast? I would try to not sharpen the tail or are the jaggies there even before sharpening after resizing? At the top of the tail it looks like the pattern of the plumage, in the middle it does look jagged.
Jaggies are there full frame Axel...I think Matthew is right relative to the plumage. Looking through my other Anhinga images that day, some taken with another camera, lens combination, I can see the same thing depending on the relative position of the tail.
Would definitely keep it. There are a lot of Anhinga images around, but not many high hey ones. I love the perfect exposure, and eye contact. I do wish for a bit less steep of an angle.
For me this is a keeper. It's nice to change it up a little bit and no always see the same types of pictures. The pose is just right and it all comes together nicely.