A modified muscular pouch immediately behind the stomach in the alimentary canal of birds, having a thick lining and often containing ingested grit, which aids in the mechanical breakdown of seeds before digestion.

• 砂囊，胗紧靠在鸟类食道的胃部后面的变化的肌肉小袋，有厚的衬层并含有摄取的砂粒，有助于在消化之前磨碎种子