I like it, Alexander! One doesn't often see bitterns this much in the open. The bird is sharp, the pose is good - I like the intensity of the stalking posture and the raised foot is a big plus. I like the composition with the OOF foreground and reflection. The image seems a bit dark overall on my monitor. I would suggest removing the odd red and yellow specular highlights from the reflection. There is an OOF blob near the left edge in front of the bird that could also be removed. Well done.
Agree with Steve. The raised foot and the reflection really make this interesting. I am not sure what the spike of grass adds, might remove it. And there's a bit of junk in the upper right hand corner.
I like this bittern a lot Alexander. From a composition standpoint, I might add a little to the top of the image if you've got it. I don't mind the single spike of grass. The blob on the left is a bit distracting to me. And a touch more USM might work. Thanks for sharing!