Mouth
As a cramorant, Thunk's digestive system starts with his beak. He has no teeth, but can bite down with the sharp edges. He must make a bobbing motion to swallow. His internal flesh is blackish grey.
Esophagus
His long esophagus makes for a perfect opportunity to show off a neck bulge. Unlike many birds, he does not have a crop, and food goes directly to the stomach.
Stomach
The stomach is like any other and digests things, and he can't bring stuff back up voluntarily.
Gizzard
The gizzard is a weak organ, made for filtering. Occasionally, once the meat is thoroughly liquified, the indigestibles like fur, bones, clothing, and the like are compressed into a pellet, and expelled out the mouth, but usually they pass along with the chyme.
The Rest
Everything else proceeds as normal, through the small intestine, the large intestine, and then out.