Pigeon (Columba Livia) – General Characters

The systematic position of Columba Livia (Pigeon)

The common name of Columba Livia is a pigeon. The group of birds is mostly medium to large stout-bodied pigeons.

The term Columba has taken from the Latin word Columba means a dove. The bird belongs to class Aves.

General Characters of Columba Livia

Habitat: Columba Livia found worldwide, lives near human habitation, on buildings, rock cuts, roofs, etc.  They are flying birds. More than 500 species of pigeon are found worldwide, and about 10 species are found in India.

Pigeon: Columba livia

                                                 Pigeon: Columba Livia

The body structure of Columba

Columba Livia possesses a boat-shaped streamlined body that is well adapted for aerial life. The body is divided into head, neck, trunk, and tail.

Head: The head of Columba is comparatively small, spherical, and situated at the anterior-most part of the body.

  • The beaks are formed by elongation of the upper and lower jaw. The jaw is without teeth. Beaks are used for ingestion, fighting, and preening of feathers.
  • Cere (external nostril) is swollen, sensitive soft skin at the base of the beak.
  • Eyes are prominent, round, and laterally present. The eyes comprise the upper and lower eyelid. A transparent membrane named the nictitating membrane is also found in the eyes of Columba.
  • The ear opening – tympanic membrane is present posterior to the eyes.

Neck: The neck is long, flexible, and cylindrical connecting the head with the trunk.

Trunk: It is spindle-shaped. The trunk bears a pair of wings and a pair of legs.

  • The cloacal aperture opens ventrally at the end of the trunk.

Tail: It is the hind part of the body. the dorsal base of the tail consists of the papilla. The papilla bears the opening of the Preen gland or Uropygial gland.

  • Preen gland: The preen gland is a cutaneous gland function for oily secretion used for lubrication or preening of feathers.
  • Wings of Columba: These are modified forelimbs. They are divided into three regions, The brachium, ante – brachium, and the manus.
  • Claws: Three clawless, imperfectly marked digits are present in each hand. Claws are used for walking and perching.
  • The forelimb is found as folded form of ‘Z’ which is extended during flight.

The Columba Livia is a warm-blooded or homeothermic organism.

The exoskeleton of Columba Livia

In pigeons, the exoskeleton is derived from the epidermis. The exoskeleton occurs in the form of horny claws, scales, and feathers.

  • Epidermal scales are present on the foot and the entire body is covered by feathers.
  • Pterylosis: Arrangement of feathers on the body of a bird.
Feathers of Columba Livia

Three types of feathers are found in Columba:

  • Large quill feathers on wings and tails are used for flight;
  • contour feathers which form a covering for the body and filoplumes, lie between the contour feathers.
  • down feathers: The nestlings are covered with down feathers and resemble the filoplumes.
Endoskeleton in Columba Livia

The skeletal system of Columba is light and strong as the bones are light and spongy in birds. Most long bones contain air instead of marrow. The air-containing bones are called Pneumatic bones. These bones reduce the weight of the body.

The breast bone also called the sternum consists of a broad plate of bone produced ventrally into a prominent ventral crest or keel for attachment of powerful flight muscles.

Flight Muscles in Columba Livia

The wings are modified forelimbs that act as organs of flight. A number of paired muscles function as flight muscles. These are the muscles that operate the wings during flight termed flight muscles.

  • The pectoral muscles are the major flight muscles of pigeons. These are of two types-
    • Pectoralis major: Large and powerful flight muscles arise from the sternum.
    • Pectoralis minor: Small and elongated and elongated muscles which elevate the wings during flight.
  • coracobrachialis muscles also help in flight they pull the wings down to rotate wings during flight.
The digestive system in Columba Livia:

The digestive system of pigeons consists long coiled alimentary canal. The alimentary canal consists following parts:

  • Buccal cavity
  • pharynx
  • oesophagus
  • crop
  • stomach
  • small intestine
  • large intestine
Digestive system in Columba livia

                        The digestive system in Columba Livia

The buccal cavity consists of a large narrow tongue with scanty papillae and numerous mucus glands. The buccal cavity leads to the pharynx through the esophagus.

The crop is a thin-walled, bilobed elastic sac and it serves as a food reservoir.

The oesophagus enters the stomach and differentiates into the anterior glandular proventriculus (which consists of a mucus lining that secrets the gastric juice) and posterior muscular ventriculus or gizzard.

  • The gizzard possesses thick and muscular walls with many tubular glands. The gizzard cavity contains grits or small pebbles called gastroliths. The gastroliths are swallowed by the birds, which helps in the grinding of food.

The gizzard leads to the small intestine. Intestine consist of ‘U’ shaped duodenum and ileum. Between the duodenum, the pancreas is situated.

The inner lining of the ileum contains numerous villi. The Villi helps in the absorption of food. The ileum leads to the large intestine.

The large intestine is short and differentiated into the rectum and cloaca.  Rectal caeca- a pair of small blind pouches, present at the junction of the ileum and rectum.

  • The rectum leads to the cloaca which divides into the anterior coprodaenum, the middle urodaenum, and the posterior proctodaeum or vestibule.
  • The rectum opens into coprodaenum
  • Urinogenital ducts open into the urodaenum.
  • The proctodaeum opens to the outside by the cloacal aperture.
Digestive glands of pigeon:

In pigeons, the buccal gland, salivary gland, gastric gland, liver, pancreas, and intestinal glands are digestive glands.

  • In pigeons the gall bladder is absent.
  • In pigeons, both sexes produce milk – a cheesy and nourishing secretion. The milk is formed by the degeneration of epithelial cells lining the crop to feed the young ones.

The bird consumed grains as food. They swallow the food, go to the crop through the esophagus, and here it is stored. The food is softening in the crop, by mixing mucus as the crop consists of mucus glands. The food then enters the stomach, ground by gizzard, and pebbles in crop and also partially digested with the help of gastric juice secreted by proventriculus. This food enters the intestine, mixed with bile and pancreatic juice for complete digestion.

Respiratory system in Columba:

The respiratory system in birds is pulmonary. The respiratory system in birds consists of the respiratory tract, respiratory organs, and air sacs.

  • The true muscular diaphragm is absent in birds.
  • The respiratory tract consists- of nares, nasal sacs, glottis, larynx, trachea, and syrinx.
  • The respiratory organs: Lungs and air sacs.

The larynx opens into the trachea which is supported by closely set rings. The trachea is divided into two bronchi, each of the bronchi divides and subdivides into smaller branches.

The lungs are solid spongy organs. These are dorsally attached to ribs. Nine air sacs are found in it. The arrangement of air sacs helps in the maintenance of high temperatures.

Syrinx: It is the structural characteristic of birds. It is the voice box found in birds at the place of the division of the trachea into two bronchi. Its walls consist of chambers supported by rings of the trachea and the first ring of each bronchus. The inner line rises into folds, by which the vibration is caused by the movement of air results in the production of sound.

The circulatory system in Pigeon (Columba Livia):

Birds possess complete double circulation including pulmonary and systematic circulation. The circulatory system of pigeons consists of the heart and blood vessels.

Heart: The heart of the pigeon is four-chambered – two auricles and two ventricles.

Heart in pigeon

                                                 Heart in pigeon

  • The two superior vanae, a post caval vein or inferior vena cava open into the right auricle
  • The pulmonary aorta arises from the right ventricle and systemic trunks arise from the left ventricle.
  • The heart is completely separated on the right side and left side by a septum.
  • The right auricle opens into the right ventricle by the right auriculo ventricular aperture and the left auricle into the left ventricle by the left auriculo ventricular aperture. Valves are present at apertures to restrict the backward flow of blood.
  • The pulmonary aorta arises from the right ventricle. The aortic arch arises from the left ventricle. In the left auricle, the pulmonary veins open. Three semilunar valves are present at the junction of the pulmonary aorta and the right ventricle.
  • The pulmonary aorta divides into two branches and each enters a lung.
  • Only the right aortic arch is present in birds.
  • Venous blood is received by the right auricle from all parts of the body except the lungs by precavel and post caval veins.
  • Venous blood is pumped into the lungs through the pulmonary aorta by the right ventricle. By Pulmonary veins the oxygenated blood returns from the lungs to the left auricle.
  • The right aortic arch carries oxygenated blood from the left ventricle to the different parts of the body.
  • The right half of the heart receives and discharges only venous blood.
  • The left half receives and discharges only arterial blood.
The nervous system in Birds (Columba)

The nervous system includes:

  • Central nervous system: Brain and spinal cord
  • Peripheral nervous system
  • Autonomous nervous system

The pigeon’s brain is rounded within the cranial cavity covered by two meninges – outer durameter and inner pia – arachnoid membrane. The space between two meninges is filled with cerebrospinal fluid.

Voluntary movements are controlled by the cerebrum, it is the center of memory and intelligence.

The diencephalon is covered by the cerebral hemisphere and cerebellum. The diencephalon passes impulses to the cerebral hemisphere, and integrates the autonomic system and perceptiveness of cold, heat pain, etc.

  • The pituitary is present in Columba.
  • Optic lobes are centers for sight.
  • The pineal body and infundibulum are present in pigeons.
Nervous system in Columba livia

                               The nervous system in Columba Livia

The cerebellum is highly developed and extends backward and covers a large part of the medulla oblongata. The medulla oblongata joins the spinal cord. Medulla oblongata controls the involuntary movements.

In these organisms, the peripheral nervous system consists of 12 pairs of cranial nerves. The spinal nerves are 38 pairs in number.

In pigeons, the autonomic nervous system consists of sympathetic and parasympathetic nervous systems.

  • Sympathetic nerves supply alimentary, respiratory, circulatory, and urinogenital systems.

Sense organs in Columba:

  • The eyes are biconvex, well-developed sense organs. A vascular pigmented part called pecten is found in the vitreous body at the point of optic nerves entering the eye. Pecten is mostly found in birds and is concerned with the power of accommodation.
  • Ear: The cochlea is well developed
  • The olfactory sense is poorly developed.
Excretion in pigeons
  • A pair of kidneys are present. These are metanephric, flat, and elongated.
  • Absence of urinary bladder
  • The nitrogenous waste is excreted as a semi-solid mass in the form of uric acid.
Reproductive system in the pigeon (Columba)

The male reproductive system consists of:

  • A pair of the testis is present. The testis is attached to the anterior end of the kidney by the peritoneum.
  • Vas deference dilates into seminal vesicle at its hind end
  • Absence of copulatory organ

Female reproductive system:

The female reproductive system consists of a single ovary on the left side and an oviduct.

  • the single ovary is an adaptation to aerial life.

 

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