Just read this thread....Hoping Wilbur is improving.
As always, Kathy is giving great advice....such a big help.
Before you massage his neck, you need to palpate it gently to see if there is anything solid in the crop. He could have swallowed a piece of rock or a tidbit of wood that has not passed on to the digestive system. You also don't want to massage too hard...if there is anything in the crop that could cause injury to his esophagus or crop. Ducks don't regurgitate things they have swallowed. The gizzard usually holds items until they are either dissolved by gastric juices or ground up by small stones the bird swallows.
If the crop is impacted, you will notice a significantly sour odor from his mouth. Since this has been going on for several days with no odor reported, I doubt Wilbur has an impacted crop.
Poly-Vi-Sol is a liquid baby vitamin. Don't purchase the liquid vitamin with iron. NO iron for poultry..
Holding good thoughts for Wilbur.