Digestive System of Birds

Digestive System of Birds

The digestive system in the birds is very basic but effective when compared to numerous other species, such as livestock. In the process of development, those bird species that developed simple but effective digestion systems were more able to fly and for this reason survive, as the simple digestion system would be lighter in weight.

Digestion is a multistep process that starts with finding food and ends when indigestible waste is expelled from the bird’s body.

Finding Food

Birds have different diet types and preferences so they find foods in different methods. They are all opportunistic feeders and will frequently sample several foods. Once a bird has found food, the consuming and absorbing procedure can begin.

Chewing and Swallowing

Birds have actually specialized bills and beaks to help them take bites, but they do not chew as human beings do. Rather, birds will either swallow food entire or if it is too large or difficult to straight swallow, they will break it into smaller sized pieces. Some birds may rip or shred food such as fruit or prey, or they will use their beaks to separate harder chunks of nuts or big seeds.


The Digestive System

The digestive system includes the alimentary canal along which the food passes after consuming to where the residual wastes are removed from the body, together with the liver and the pancreas. The digestive system is accountable for the ingestion of food, its breakdown into its constituent nutrients and their absorption into the bloodstream, and the elimination of wastes from this process.

The liver produces bile and is related to the metabolism of nutrients together with a variety of other functions. The main function of the pancreas is the production of digestive enzymes and special substances called hormones.

Saliva and Salivary Glands

Some birds have quite functional salivary glands and in birds that feed mainly on small bugs or seeds– bird saliva is utilized to glue the insects or seeds into a sticky ball for ease of swallowing. Though in some birds such as the pelicans, the salivary glands have actually vanished altogether.

The most widely known salivary glands in birds are those of the swifts and swallows, which are used not just in consuming, however also in gluing together the components utilized to develop the nest. The salivary glands are:

  • Maxillary— in the roofing of the mouth.
  • Palatine— on either side of the nasal opening in the roof of the mouth.
  • Apheno-pterygoid glands– in the roofing of the throat on each side of the typical opening for the eustachian tubes (the eustachian tubes link the middle ear to the mouth and their function is to equalize the air pressure on each side of the tympanic membrane in the ear).
  • Anterior sub-mandible glands— in the angle formed by the union of the upper and lower beaks or mandibles.
  • Posterior sub-mandibular glands.
  • Linguistic glands— in the tongue.
  • Crico-arytenoid glands– around the glottis.
  • A small gland in the angle of the mouth.
The alimentary canal

The alimentary canal is a long tube-like organ that starts at the beak and ends with the vent or cloaca in the stomach. Glands that produce essential digestion juices are found in various places of the canal. The nutrients from the food, after digestion, are taken in through the wall of the alimentary canal into the circulatory system for transport to the liver or other parts of the body.


In lots of birds, the esophagus ends in a specialized storage organ called the crop. This is generally just an enlarged part of the esophagus… where food consumed in a hurry to avoid predators is kept until it can be digested later. The crop is an out-pocketing of the esophagus and is located simply outside the body cavity in the neck region.

Swallowed feed and water are saved in the crop till they are passed to the rest of the digestive tract. When the crop is empty or nearly empty, it sends hunger signals to the brain so that the bird will eat more.

Gizzard and Stomach

The ventriculus, or gizzard, is a part of the digestive system of birds, reptiles, earthworms, and fish. Typically referred to as the mechanical stomach, the gizzard is made up of two sets of strong muscles that act as the bird’s teeth and have a thick lining that safeguards those muscles. Consumed feed and the gastrointestinal juices from the salivary glands and proventriculus enter the gizzard for grinding, mixing, and mashing.

The glandular stomach gets food from the esophagus and produces mucus, HCl, and pepsinogen, similar to what is seen in the mammalian stomach. A complex cycle of contractions involving the two stomachs force-feeds backward and forward between the two, grinding it and increasing direct exposure to gastrointestinal enzymes.

Small Intestine

Birds have a small intestine that seems very similar to the small intestine of mammals. A duodenum, jejunum, and ileum are defined, although these sectors are not as histologically distinct as in mammals. The proximal small intestine gets bile from the liver and digestive enzymes from the pancreas, and the absorptive epithelial cells are decorated with basically the very same enzymes and transporters as in mammals.

Large Intestine

The large intestine includes a short colon and, normally, a set of ceca. Short villi extend into the lumen of the colon, unlike which is present in mammals.


The large intestine terminates in the front part of the cloaca. The cloaca is a tubular cavity opening to the outside of the body and is common to the digestion and urogenital tract. The structure of the cloaca is really similar to that of the intestine other than that the muscular is mucosa disappears near the vent.