(iii) Class - Aves

Class Aves, commonly known as birds, represents a group of warm-blooded vertebrates characterised by feathers, beaks, and the ability to fly.

They are highly adapted for aerial locomotion and exhibit a wide range of ecological and behavioural diversity.


General Characteristics:

  • Birds have a lightweight, streamlined body covered in feathers, which provide insulation, flight, and display purposes.
  • They possess a beak without teeth and modified forelimbs as wings.
  • Birds are endothermic, maintaining a constant body temperature through metabolic heat production.



  • Birds have a unique respiratory system with air sacs, allowing for efficient gas exchange during flight.
  • They possess lungs, but air flows unidirectionally through the respiratory system, facilitated by the air sacs.


Feeding Habits:

  • Birds exhibit diverse feeding habits, including herbivory, carnivory, omnivory, and filter feeding.
  • Beak structures are adapted to the specific dietary preferences of each species.


Circulatory System:

  • Birds have a four-chambered heart, similar to mammals, which efficiently pumps oxygenated blood to the body.
  • Their high metabolic rate requires a well-developed cardiovascular system.



  • Birds excrete nitrogenous wastes primarily in the form of uric acid, which helps conserve water.
  • Uric acid is excreted along with faeces as a semisolid substance.



  • Birds exhibit internal fertilisation and lay eggs with hard calcareous shells.
  • They have a highly developed parental care behaviour, including nest-building, incubation of eggs, and feeding of young ones.


Economic Importance:

  • Birds have immense ecological importance as pollinators, seed dispersers, and regulators of pest populations.
  • Some species of birds are domesticated for food production, such as chickens and ducks.
  • Birds are also widely studied for their behaviour, migration patterns, and as indicators of environmental health.



  • Pigeon (Columba livia)
  • Peacock (Pavo cristatus)
  • Crow (Corvus splendens)
  • Sparrow (Passer domesticus)
  • Eagle (multiple species, e.g., Aquila chrysaetos)
  • Ostrich (Struthio camelus)
  • Emu (Dromaius novaehollandiae)
  • Penguin (multiple species, e.g., Aptenodytes forsteri)
  • Parrot (multiple species, e.g., Psittacus erithacus)
  • Kingfisher (multiple species, e.g., Alcedo atthis)