I agree with Svante about cropping to only include the flapping bird. The side-lighting makes your exposure more of an issue. The birds seem a little soft to me, and I wonder if the focus has fallen on the background vegetation. Where was your active focus point?
Looks like spring is slowly coming where you live Jeroen. I think you have the foundation of a good image here but it will need some post-processing. I agree with leaving out the right hand bird, and I would leave out the ducks too. If you had eye-contact with the bird you could leave it in of course but it's just not strong enough without. If you crop to focus on the lefthand bird you will need to add a little room to the left so that the wing-tips are not so close to the edge of the image. In processing the image you will need to tone down the whites some. Finally another round of sharpening is needed. If you tackle a re-work we would be interested to see the results.