What a gorgeous bird! The whites on the neck may be a little hot. I would take a tad off the bottom. As mentioned great isolation and very nice background. Would love to see more of these.
Good comments above, but I can see some texture in the whites, and suspect they are not blown. Lovely duck.
I would consider toning down the brightness of the brown areas in the upper background just to keep our eyes from being pulled away from the duck. Won' take much.
The whites look fine from here despite the somewhat harsh light. Here is a case where the chosen perspective is too low: by getting down almost to water level the distracting white BKGR elements were introduced.
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Good look at the handsome duck. Whites look OK to me too and I agree a bit higher to even out the BG would have been good. Image looks to need a CCW rotation.
Handsome drake. The whites look good from here too. Good suggestions already made. You could choose to tone down those white areas during PP, but I agree getting it done in-camera is almost always best.