The most important functions of the intake of substances, their conversion and removal of undigested residues from the body are performed by the digestive system. Birds, being animals adapted for flight, possess certain features of the internal structure. They are primarily aimed at reducing their body weight. The digestive system is no exception.
Digestive system of animals
All chordates, which include birds, have a similar structure of the digestive system. It begins with the oral cavity. Then, through the throat, food enters the esophagus - the tube leading to the stomach. This part of the digestive system is an expansion in which food has been present for quite some time. The final absorption of nutrients occurs in the small intestine, and the removal of undigested food residues is carried out by the final section of the tract. It is called the large intestine, opening outward with a cloaca or anus.
Features of the digestive system of birds are the presence of goiter - the expansion of the esophagus and a decrease in the length of the intestine. These structural features contribute to more intensive digestion of food and reduce body weight of birds.
The same can be said of other organ systems?
The internal structure of the birds (table).
| Organ system | Structural features |
| Breathing | Presented by the respiratory tract (nasal cavity, larynx, trachea, bronchi), lungs and air sacs |
| Circulatory | A four-chamber heart (two atria and two ventricles) and a closed system of blood vessels. The birds have two circles of blood circulation: large and small. Due to this, venous and arterial blood does not mix, and birds are warm-blooded animals. Thus, their body temperature is independent of ambient temperature. |
| Excretory | It consists of paired kidneys and ureters, the ducts of which open in the cloaca. |
| Nervous | The spinal cord and brain, of which the cerebellum is most developed. |
| Sexual | Birds are dioecious animals. The reproductive system is represented by the sex glands: the testes in males and the unpaired ovary in females, which also serves as a condition for reducing their mass. |
What do birds eat?
The structure possessed by the digestive system of the bird, its features and differences, primarily due to the nature of the food. City dwellers feed on insects, seeds, and leftovers from human food.
The taste preferences of birds are quite diverse. Seagulls drink salt water, filtering it through the glands.
The poisonous bird flycatcher is also due to the characteristics of the food. She consumes beetles. Their poison penetrates the skin and feathers of birds. Although the flycatcher itself has a stable immunity to its action. A person may get burned by touching it. But very small animals die from the harmful effects of flytrap toxins.
Birds that live in natural conditions eat tasty fruits, small vertebrates, and even carrion. To do this, they have all the devices.
Beak
Birds do not have teeth. But they can easily cope with hard nuts and small seeds. After all, it was the beak that originally performed the function of the teeth. With its help, birds chop, crush or tear food. The beak consists of a solid horn-like substance that can withstand a fairly large weight and prolonged loads. For example, a forest woodpecker can make a hole up to 10 cm deep in the bark of trees to enjoy insect larvae.
The shape and size of the beak depends on what the birds eat.
For example, predators have a large curved beak, with the help of which they can easily grab and tear the prey. Peregrine Falcon attacks even large foxes and wolves. Forest birds, extracting insects from the bark of trees, like a chisel, make holes in it.
The tongue located in the oral cavity also helps to get food. It has special keratinized papillae that help keep food in the oral cavity.
The bird’s digestive system continues through the throat, with the help of which the partially processed food moves along the path.
Esophagus and goiter
The bird's esophagus has an unusual structure. It is not just a tube leading to the stomach. It forms an extension called goiter. It is here that food is delayed for a certain time and is chemically treated with saliva. And seagulls and pelicans transfer forage to the chicks from the place of feeding to the nests.
What is bird milk
The name of this delicious dessert is familiar to everyone since childhood. It got its name due to the outward resemblance to a substance that only birds can isolate.
Some birds in specialized goiter glands produce a nutritious foamy mass. They use this valuable product for feeding chicks.
Bird's milk has nothing to do with animal milk. It is not liquid at all, but looks like a whipped curd mass. But it also contains many valuable organic substances and vitamins that can provide the newborn with everything necessary.
In penguins, bird milk is formed in the stomach, and not in the esophagus, it is most rich in fats. This substance is necessary for the development of chicks in difficult northern conditions. And adult penguins use the fatty layer not only to warm the body, but also as a supply of food and energy. Hatching the chicks for several months, the males do not leave the place of masonry. In this state, they simply are not able to get food and maintain viability due to subcutaneous stores.
Features of the structure of the stomach of birds
The stomach of birds also has characteristic features. It consists of two parts.
The departments of the stomach are called glandular and muscular. In the first, food is processed by gastric juice, i.e. here its chemical treatment continues. The surface of the muscular section is covered with a film of keratinized substance. With its help, food is rubbed to a mushy state.
Surely many saw birds pecking at small pebbles. They do this not at all because they do not know about their taste. Once in the muscular part of the intestine, the stones contribute to the mechanical grinding of coarse food. Thus, the absence of teeth in birds is compensated.
Intestines
From the stomach, processed food enters the small intestine, into which the ducts of the liver and pancreas open. In this part of the digestive system, food is finally digested and absorbed into the blood.
Outwardly, the intestine opens with cesspool. It is a hole through which undigested food residues, products of the functioning of the reproductive and excretory systems are removed.
A feature of the structure of the intestine is its small length. It depends on the nature of the food. For example, in birds that prefer plant foods, the intestines are 8 times longer than the body. And the insectivorous representatives of birds - only 4.
By the way, the most gluttonous bird is considered - the record holder of the smallest sizes. Guessed? Well, of course, it's a hummingbird. For a day, she is able to consume pollen, whose weight is 2 times her own weight.
And the wren in one day brings the chicks up to 500 caterpillars and insects. What an appetite!
And vultures are winners among the most greedy and insatiable creatures. With a large amount of food, they eat so much that it is simply impossible for them to fly up. Vultures solve this problem in a natural way: they wait until body weight decreases.
Birds digest food intensively, quickly emptying the intestines. This helps to reduce their body weight and provide the body with the right amount of energy. An ordinary sparrow can digest a caterpillar in 15 minutes, and grain in 3 hours. That is why birds spend most of their lives in search of food.
Digestive glands
Salivary, pancreas, and liver are the list of digestive glands that birds have. They secrete biologically active substances - enzymes. They accelerate the digestion process by breaking down complex carbohydrates to monosaccharides, proteins to amino acids, lipids to glycerol and fatty acids. It is in this form that organic substances can be absorbed by the body.
Features of the digestion of birds
The internal structure of the birds (the table is presented in the article) indicates that all the features of their anatomical organization are aimed at adapting to flight. This also applies to the digestive system.
Instead of cheeks and lips, birds have a beak, with the help of which food is captured and held. The oral cavity has a hard palate. It is covered by the mucous membrane, on which there are special cone-shaped papillae. With their help, the feed moves into the esophagus. So that food does not enter the nasal cavity, palatine muscles already make the palatine gap.
The departments of the stomach that perform different functions contribute to the intensive processing of food. The intestine consists of two sections - thin and thick.
The digestive system of the bird provides all the vital processes of birds. And the features of its structure determine the ability of these amazing animals to fly.