The digestive system of the birds includes more regions than ours. The first region is the beak with the fleshy tongue, followed by the esophagus. As seed-eaters, budgies have a crop. This is a sack-like pouch of the esophagus located at its lower section. The crop fulfills two different tasks: First, the food is moistened in it, but the actual digestion doesn’t take place there. Secondly, it serves to store the food so that the birds can feed their partners or their chicks with it.
After the food could soak for some time inside the crop, it is carried on into the two-part stomach. At first, the food reaches the glandular stomach which is also called proventriculus. This part of the bird’s anatomy secretes hydrochloric acid and pepsinogen to predigest the food. In the next step, the predigested food is mechanically kneaded and split into tiny components. It’s the gizzard, also referred to as the ventriculus, that performs this task.
This mechanical crushing is supported by tiny pebbles that should be regularly picked up by the birds who eat seeds. Therefore, a bowl filled with mineral grit or bird sand should never be missing. Only birds who are fed with extruded food do not necessarily need grit or sand. Many bird owners don’t offer bird sand and grit, because they are afraid their budgies will eat too much of it and as a result suffer from a blockage of the crop, ventriculus, or proventriculus. But by keeping the birds away from these digestive stones, one may harm the animals under some circumstances. Indeed, the birds need small particles for healthy digestion. If a bird eats too much grit, this could be due to an early stage of a disease, which the animal would like to relieve itself.
The gizzard is followed by the first section of the small intestine, into which the excretory ducts of the pancreas open. Pancreatic enzymes play a decisive role, especially in the digestion of starch and fats. If the pancreas is not working properly, health problems such as inflammation of this organ can occur.
The intestine of the birds is comparatively short, from what a low dwell-time of the digested food in this region of the digestive tract results. At its end, the bird’s intestine merges into a small cavity: the cloaca. The ureters and the connections to the sexual organs also lead to this part of the body. In birds, the posterior opening of the cloaca is the only excretory organ. Feces, urine, and sperm or eggs leave their body through it.
By the way: Among scientists, it is considered as a secured fact that birds have two stomachs because the retention period of the food is extremely short thereby in each of the highly specialized regions of their body. This is of great importance for birds because they have to get as much energy as possible from the food without being impaired in their flight ability for too long by the extra weight of the food.