What is the gizzard in birds primarily responsible for?

• A. Grinding up food that the bird has eaten
• B. Storing bile
• C. Filtering blood
• D. Producing enzymes

Answer: (A)

Birds lack teeth, so they rely on a muscular stomach called the gizzard to break down food. It acts like a grinding mill, often using swallowed stones to physically pulverize seeds, tough plant matter, and other food. This grinding is the primary job of the gizzard and it makes digestion more efficient by increasing the surface area for further chemical digestion later in the tract. The other options describe functions handled by different parts of the body: storing bile is a biliary function, not grinding; filtering blood is done by organs like the liver and kidneys; producing enzymes is mainly done by glandular stomach tissue (and the pancreas). So the best answer is grinding up food that the bird has eaten.