This is a picture of the mouth of the wood duck. Notice the different sections and structures associated with the mouth.  The tongue is on the floor of the mouth.
 
 

    This is a picture of the esophagus which contains an expanded are known as the crop.  There are structures around the esophagus that are labeled as well.
 
 

    This is the inside of the crop.  Notice how the walls look keratinized and how this structure looks like a muscular organ.  This is where food is temporarily stored.