Final answer:
In avian species, the ventral wall of the esophagus expands to form the crop, which stores food before it is digested. The crop is not the cloaca, which serves as a common opening for excretion and reproduction.
Step-by-step explanation:
In avian species, the ventral wall of the esophagus is greatly expanded to form a pouch called the crop, which stores food. This structure allows birds to consume food quickly and store it for later digestion. The food passes from the crop to the proventriculus, a glandular part of the stomach that secretes digestive juices. From there, it moves to the gizzard, a muscular part of the stomach that grinds the food, often with the help of ingested stones or grit. The cloaca is an opening in birds used for the excretion of waste from both the digestive and excretory systems, as well as for reproductive purposes, but it is not involved in the initial storage or digestion of food.