Columba livia, the pigeon included in:
Phylum – Chordata,
Sub-phylum – Vertebrata,
Class – Aves.
The body is spindle shaped. The size varies from 20-25 cm. The body is divisible into head, neck, trunk and tail. Most part of the body is clothed in feathers.
The head is small and rounded. It is anteriorly pointed into a short beak. The head contains the following structure.
It is the wide gap at the anterior end of the head and is bounded by upper and lower beaks.Both the beaks are covered by a sheath called horny sheath or rhamphothecae.
At the base of upper beak occurs a pir of whitish swollen area of soft skin, called cere.
Just anterior to the cere, a pair of external nares are present as minute slits.
On each lateral side a pair of prominent eyes are present. Each eye is provided with an upper, a lower and a movable transparent third eyelid or nictitating membrane which runs across the eyeball.
These are small apertures on the posterior side of the eyes. Each aperture remains covered by a special group of feathers called auricular feathers. Each aperture leads to a canal called external auditory meatus which is closed below by the tympanic membrane.
The neck is long and flexible. Its flexible nature is responsible for the universal movement of the head.
It is the greatest and widest part of the body. It is boat shaped. At the hind end of the trunk is the cloacal aperture. The trunk bears a pair of wings and pair of legs.
The forelimbs are modified into wings. Each wing consist of 3 parts: branchium (upper arm), antebranchium (fore arm) and manus (hand) with 3 fingers.while at rest the three divisions are folded in the form of Z during flight they are extended. Between anterior portion the branchium and antebranchium is a fold of skin called the alar membrane or pre-patagium. Between posterior portion of the branchium and trunk is a small fold of skin called post patagium. The hind limbs are adapted to balance and support the entire weight of the body at rest. Each hind limbs consists of 3 parts, Femur (thigh), crus (shank) and pes (foot) with four toes. The first toe or hallux is directed backwards the remaining three forwards. The feet are adapted for perching with long toes and curved claws. The entire foot is covered with horny epidermal scales.
The tail is a conical projection behind the cloacal aperture. Dorsally the avian skin of tail bears an oil gland or preen gland or uropygeal gland that secrets an oil by the bird to preen its feather. It is best developed in water birds.
The exoskeletons of birds include beak, claws, spurs scales and feathers. The beak is heavily keratinized structure. The claws are epidermal derivatives that lie on the toes.t spurs of game cocks are horny spines covering bony cores.t epidermal scalesr limited to the feet and base of beak of the birds. The feathers, the appendages of avian skin, are also heavily keratinized. The keratin of avian skin is α-keratin. The feathers are evolved from the epidermal scales of reptilian ancestors. The feathers contain β-keratin which is the same type of keratin that occurs in the outer surface of scales of reptilian ancestors. The arrangement of feathers on the body is called pterylosis. The feathers are arranged in definite tracts or areas. These tracts are separated by feathersless area called apteria. The feathers are of 3 types: quill feathers, contour feathers and filoplumes.
The Quill feathers are located on the wings that help in flight are called reminges or wing quill and those are present on the tail are termed as rectices (12 in number in pigeon). The retrices help the bird as a brake and in stearing the flight.
Most familiar and complex are the contour feathers. They are located all over the body except at the wings and tail. They give the bird its external form(contour) and provide airfoils for the flight.
Filoplume or Hair Feathers:
These are present along the contour feathers.
In nestlings (young birds in the nest) down feathers are present as temporary covering. In some species down feathers are hidden by contour feathers, are widely distributed and not restricted to pterylae. Their function is insulation.