2,544. The Digestive Organs of a Bird
Hilchos Shechita 6:17
A bird doesn’t have a rumen, omasum or reticulum; it has a crop and a craw. Everything that causes an animal to become a treifa applies to domesticated animals, wild animals and birds. If the roof of the crop is punctured even the smallest amount, the bird is a treifa. The roof of the crop is the part that stretches out with the esophagus when the bird extends its neck. If any other part of the crop is punctured, the bird remains permitted.
Hilchos Shechita 6:18
The craw has two coverings; the outer is red like meat and the inner is white like skin. If only one gets punctured, the bird remains permitted; it isn’t prohibited unless both are punctured, if only a little. If both are perforated in different places so that the holes don’t line up, the bird remains permitted.