I have been photographing Ruby Throats since 2007. I am not a flash guy nor will I ever be. Image taken 2013-06-23. My back yard. Exif data Canon IS f2.8 300mm with a 20mm ET, f6.3, 1/2000, ISO 1600
It's very nice to get a hummingbird drinking out of a flower. I've had no success with it.
You got a pleasing wing blur and the bird looks sharp, although without the extra light of flash you are limited to a narrow DOF with these little guys. Full sun was probably the best option to get enough light, but the shadow on the head is a minus for me, as are the OOF flowers in the FG. Have you tried using a reflector to get light into the shadows? A large piece of cardboard with slightly-wrinkled aluminum foil glued on it is wonderful. That might allow you a little narrower aperture, too.
Although this is an excellent available light image and is well exposed and sharp, the harsh shadows on the beak and head really hurt. Flash would have really helped here. The correct use of flash is an excellent tool in nature photography and refusing to use it is a detriment in my opinion.
Comp, rich colours, details all look good to me. I love that you have a bit of detail even in the blurred wing. Nice iridescence on the gorget too. I agree the shadow is unfortunate, and because you do not use flash Diane's suggestion is worth considering.