The Muscular Part of a Bird’s Stomach
Puzzle 7 of Buying Books Piece of Cake Pack
Question is: The Muscular Part of a Bird’s Stomach
and the answer is: GIZZARD
Word Meaning:
GIZZARD — A specialized organ constructed of thick muscular walls found in the digestive tract of some animals, including archosaurs (including crocodilians and birds), earthworms, some gastropods, some fish, and some crustaceans, and used for grinding up food, often aided by particles of stone or grit.
Definitions from Wiktionary.