Cool-looking bird, I'd love to see some of these sometime. I would desaturate the sky and it looks as if there is a slight color cast and there are some artifacts in the sky, probably from jpg compression. I would run Viveza if you have it to bring out more details in the blacks and to tone down the highlights more.
Tropic birds are awesome to photograph on Midway. I have some great memories of these guys. The congregate near shore where they ground nest for aerial courtship displays.
Agree 100% with Axel's recommendations. Good exposure with the highlights, white birds in full sun can be a challenge for most people. Sharpness is good also.