One of my favorite spots to take pictures is Leroy Percy State PArk in Mississippi. Despite the fact RWBLs are not the most popular birds I like these fellows thousand and thousand of them migrate to MS to overwinter there.
1D MkII 4.0;500mm ISO 800 f=10 1/1250sec Av - 0.7 high-speed fill-flash (flash near the water -0.7)
I know the background is not the best but the swamp at this spot is a pretty tricky to set up the tripod and quite cold for the photographer in winter :-)
Great shot, if it were mine I would blend or clone the highlights at the top and possibly brush the buff coloured stripe to blend that a little also. Other than those minor nits I think it is excellent.
Nice capture and interesting action pose. Good use of flash and exposure and colours on the bird are amazing. I would also consider toning down the highlights and noise reduction on the background.