General Characteristics

Birds are feathered vertebrates. Females lay hard - shelled amniotic edges.

Birds have beaks for food gathering.

• With over 10,000 species of birds found in 28 orders, 163 families and 1,975 genera, most people will be able to tell you at least one characteristic of birds.
• Birds are warm-blooded homeothermic, also called endothermic i.e. they have more or less constant body temperature.
• Birds have body covered with feathers and scales they are present only on hind-limbs.
• Birds have Jaws with horny beak and no teeth.
• Forelimbs modified into wings for flight.
• Only left ovary and oviduct present in the females.
• All oviparous (lay eggs), egg with much yolk and calcareous shell.

External and Internal Features (adaptations) in birds

Birds constitute a well defined group of vertebrate animals, especially designed and adapted for aerial mode of life. They evolved not only wings, but also many other adaptations that make it possible to fly.

Morphological adaptations

Body shape

• Birds have short, light and compact body as compared to other animals.

Compact body

• The body is compact and light, strong dorsally and heavier ventrally. Attachment of wings high on the thorax.

Body Covered With Feathers

The feathers are smooth, directed backwards, and closely fitting which make the body streamlined and reduce friction during flight.

Forelimbs Modified into Wings

The forelimbs of birds are modified into wings which are adopted for flight. These consist of a framework of bones, muscles, nerves, feathers, and blood vessels.

Perching

When a bird sits on the branch of a tree, its toes wrap around the twig. This is known as perching. The muscles are so well-developed that a bird can sleep in that position without falling.

Short Tail

The tail bears long feathers that spread like a fan and function as a rudder during flight. They also function in balancing, lifting, and steering while flying and perching.

Beak

Beak compensate the function of forelimbs.

Mobile Neck and Head

The birds have a long and flexible neck which helps in the movement of head important for various functions.

Bipedal Locomotion

Due to the modification of forelimb into wings, hindlimbs balance and support the entire weight of the body.

Flight muscles

• Flight muscles are enormous as they have to generate thrust and vigorous movement of wings during flight.
• Flight muscles on the breast are greatly developed.
• Pectoralis major lowers the wings.
• Pectoralis minor elevates the wings.