Actually if there is a need for the horizon to be straight it is small as the real horizon is way back there, the dark blue line and that is straight.

Using the building as a reference it between 6 to 10 degrees... I would not bother with it...

I also disagree with the cropping. You are taking the bird out of context and bring the building into prominence.

Mooseyes does a great job at correcting the crop but at an enormous cost to the bird.

The picture itself (Original) must be gorgeous as everything is in focus, saturated and so forth. Don't see why you would want to mess with it.

I found something odd while looking 1:1 There is a multi-pixels bright red spot. Check your pictures to see if you see it on regular basis. It maybe a defect on the sensor...

I did a search on this and this is what came out:
http://www.kenrockwell.com/tech/hot-pixels/index.htm#
http://www.slashgear.com/how-to-remove-stuck-pixel-on-your-digital-slr-2227392/

Did not see any grain (and I looked after you mentioned it). If you are looking at the sky, this is normal. All sensors dislike this type of haze.

Well, since someone else jumped in with a post of a suggested "fix", I thought I would see what I could come up with. First, the angle of the shot is what makes the shore line look off; however, if you were to plumb line the bird it looks pretty straight as is. That being said, I did do a very minor clockwise rotation (1.5 degrees) to give me a better crop line on the left, so those distractions could be removed. Because the left line was too close to the bird, I felt that an edge treatment that "bit" into the bird just a touch gave it an overall better feel.

I cropped down into the background building, wanting to get rid of the distracting colored roof in an attempt to make the background go away even more (reducing the aspect ratio of background to primary subject).

The floating thing in the water was removed.

Finally, the levels were off. I adjusted and lightened, after sharping edges.

The subject really is the focus now, and seems to almost pop out to the viewer. The resulting comp. really seems to make this a much stronger image.

I hope you agree. In any event, you caught a stunning shot of this "drop-in" critter! Super grab shot. . .well done.

Well, since someone else jumped in with a post of a suggested "fix", I thought I would see what I could come up with. First, the angle of the shot is what makes the shore line look off; however, if you were to plumb line the bird it looks pretty straight as is. That being said, I did do a very minor clockwise rotation (1.5 degrees) to give me a better crop line on the left, so those distractions could be removed. Because the left line was too close to the bird, I felt that an edge treatment that "bit" into the bird just a touch gave it an overall better feel.

I cropped down into the background building, wanting to get rid of the distracting colored roof in an attempt to make the background go away even more (reducing the aspect ratio of background to primary subject).

The floating thing in the water was removed.

Finally, the levels were off. I adjusted and lightened, after sharping edges.

The subject really is the focus now, and seems to almost pop out to the viewer. The resulting comp. really seems to make this a much stronger image.

I hope you agree. In any event, you caught a stunning shot of this "drop-in" critter! Super grab shot. . .well done.