Birds (Class aves) are the best known and most easily recognized of all animals. Birds have mixed with mankind in every aspect of life. They are unique in having feathers for flying which also cloth and insulate their bodies to make possible a regulated body temperature. They have easily avoided all kinds of enemies on land by adopting an aerial mode of life. The distinctive colouration and voices of birds appeal to human eyes and ears. Many birds are of economic importance because of their food habits. Certain kinds are hunted as game and few domesticated species contribute to man’s food. Chickens are modern delicacies of the table.

Birds (Class aves) represent significant advance over all lower vertebrates in having

  1. An insulated body covering,
  2. Complete separation of veinous and arterial circulation in the heart
  3. Regulated body temperature
  4. High metabolic rate
  5. Highly developed voice, sight and hearing
  6. The ability to fly.

Birds (Class aves) occupy all continents, oceans and islands, penetrating the Arctic beyond 800 N and the Antarctic, and live from sea level to above timber line on the Everest. They fully obey the laws of animal distribution. Albatrosses live in open ocean, ducks on marshy places, savanna, sparrows live on grasses, woodpeckers and others live on trees, and so on. In polar regions only few species are found. In temperate lands 150 to 200 kinds of birds may be found in localities at various seasons. Birds have well adapted migratory habits. They fly thousands of miles for breeding and nesting. Primitive people used wild birds for food and garments. Ducks, herons and other birds have been used as game. Feathers of birds provide ornaments to modern women and are also used in sports material.


  •  Body covered with feathers.
  • Forelimbs modified as wings.
  • Adapted for flight and aerial mode of life.
  • Mouth formed by beak.
  • Single occipital condyle.
  • Heart 4-chambered. Lungs compact with air sacs.
  • No urinary bladder.
  • Excretory waste as uric acid.



SUB-CLASS A :- Archaeornithes​​

  • Link between reptiles and birds.
  • Both jaws contained teeth in sockets.
  • Wings broadly flattened.
  • Fingers 3, each with claw. No pygostyle.
    Example :- Archaeopteryx (extinct)

Sub-class B :- Neornithes

  • True birds.
  • Metacarpals fused. Sternum keeled.

Super-order 1. Odontognathae

  • New world extinct toothed birds.
  • Clavicles not fused. Sternum without keel.
  • Wings of vestigial humerus.
    Example :- Extinct Hesperomis, Ichthyomis.

Super-order 2. Impennae

Order 1. Sphenisciformes

  • Forelimbs (wings) paddle-like.
  • Bones much compressed. Tarsometatarsus incompletely fused.
  • Found in Antarctica and Galapago islands.
    Example :- Penguins. Aptenodytes jorsteri, A. sphenisu.

Super-order 3. Palaeognathae

  • Walking birds. No teeth. Wings reduced. Flightless.
  • Coracoid and lower scapula small, usually fused.

Order 1. Struthioniformes

  • Flightless, terrestrial and sternum without keel.
  • Pubic symphysis present. Feathers without aftershafts.
    Example :- Ostriches (Struthio)

Order 2. Causuariformes

  • Flightless, terrestrial and sternum unkeeled. 3 front toes on each foot.
  • Wings small. Neck and body densely feathered.
    Example :- Cassowaries (Casaurius dromocilus) and Emus

Order 3. Aepyornithiformes

  • Flightless. Sternum short, broad and unkeeled.
  • Wings vestigial. 4 toes.
    Example :- Extinct elephant bird (Aepyomis).

Order 4. Dinornithiformes

  • Flightless, terrestrial. Sternum reduced and unkeeled.
  • Coracoid, scapula and wing bones reduced or absent.
  • Hind limbs massive. 3 or 4 toes.
    Example :- Extinct moas (Dinomis).

Order 5. Apterygiformes

  • Flightless, terrestrial. Bill long and slender.
  • Wings degenerated. Humerus vestigial. Feathers with large aftershafts.
    Example :- Kiwis (Apteryx).

Order 6. Rheiformes

  • Flightless, terrestrial and sternum unkeeled.
  • Head and neck partly feathered. Feathers lack aftershaft.
    Example :- Rheas (Rhea).

Order 7. Tinamiformes

  • Sternum keeled. Tail short. Pygostyle reduced.
  • Wings short, rounded and developed for flight.
    Example :- Tinamus, Rhynchus

Super-order 4. Neognatbae or Carinatae

  • Modern birds. New jaw formed by beak without teeth.
  • Sternum keeled. Wings well-developed.

Order 1. Gaviiformes

  • Legs short. Toes fully webbed. Patella reduced.
  • Tail has 18-20 stiff feathers. Hight swift. Example :- Loons (Gavia).

Order 2. Podicipediformes

  • Tail tuft of downy feathers.
  • Legs far back on body. Feet lobed.
    Example :- Grebes (Podiceps, Podilymbus).

Order 3. Procellariformes

  • Nostrils tubular. Bill covered by horny sheath.
  • Plumage compact, oily in texture.
    Example :- Albatrosses, Fulmars, and Petrels. Diomedea, Oceanodroma.

Order 4. Pelecaniformes

  • All 4 toes included in footweb.
  • Nostrils vestigial or absent.
    Example :- Pelicans, Cormorants, Boobies and Ganuets. Pelecanus, Phalacrocorax, Sula, Moras.

Order 5. Ciconiiformes

  •  Long-necked and long-legged wading birds.
  • Decorative plumes. Bill abruptly decurved.
    Example :- Herons, Storks, Thies and Harningo. Ardea, Butorides, Egretta ciconia, Phoenicopterus.

Order 6. Anseriformes

  • Bill broadened with horny ridges.
  • Tongue fleshy, legs short and feet webbed.
    Example :- Ducks, Geese and Swans. Anas, Anser, Cycymas, Aythya, Brent.

Order 7. Falconiformes

  • Bill stout, hooked at tip with soft naked skin (cere) at base.
  • Feet adapted for grasping with sharp curved claws.
    Example :- Vultures, Kites, Hawks, Falcons and Eagles. Athanis auria, oragyps, Neophoros, Nephoros, Porenopterus, Milvus.

Order 8. Galliformes

  • Bill short, feathers with aftershaft.
  • Feet usually adapted for scratching and running. Game birds.
    Example :- Grouse, Quail, Pheasants, Turkeys. Gallus, Lagopus, Opisthoconus, Francollinus, Centropus, Pavo cristatus.

Order 9. Gruiformes

  • Feathers with aftershaft.
  • Weak or strong flight.
    Example :- Games, Rails and Coots. Rallus, Fulica, Gollinula, Porphyrio, Antigone, Anthropoides and Gus canadiensis.

Order 10. Diatrymiformes

  • Bill huge. Wings atrophied.
  • 4 toes on each feet.
    Example :- Diatryma (extinct).

Order 11. Charadriiformes

  • Toes webbed.
  • Plumage dense and fum.
    Example :- Shore birds, Waders, gulls. Charadrius vociferous, Capella, Larus, Philohela, Erolia.

Order 12. Columbiformes

  • Bill short and slender.
  • Tarsus shorter than toes. Crop producing pigeon milk for young ones.
    Example :- Pigeons and Doves. Columba livia, Columbajasciata, Ectopistes, Zenaidura, Crocopus and Streptopelia.

Order 13. Cuculiformes

  • Toes 2 infront and 2 behind.
  • Feet not adapted for grasping. Tail long. Bill moderate.
    Example :- Cuckoos. Coccyzus, Cuculus, Eudynamis

Order 14. Psittaciformes

  • Beaks stout, narrow, sharp-edged and hooked.
  • Plumage brilliant green blue, yellow or red.
    Example :- Parrots and Parakeets. Psittacula, Rhynchopsitta, Pachyrhyncha

Order 15. Strigiformes

  • Head large and rounded.
  • Eyes large and directed forwards. Nocturnal.
    Example :- Owls. Tylo alba, Bubo bubo, Otus, Nyctea, Scandiaca

Order 16. Caprimulgiformes

  • Bill small and delicate.
  • Legs and feet small. Weak and adapteC for grasping.
    Example :- Goatsuckers, Night jars. Antrostomus, Phalaenoptilus.

Order 17. Apodiformes

  • Smallest birds. Legs very short and feet very small.
  • Bill small and weak.
    Example :- Humming birds and Swifts. Chaetura, Adagica, Micropus

Order 18. Colliformes

  •  Small passer like.
  • First and fourth toes reversible. Tail very long.
    Example :- Colies (mouse birds). Colius

Order 19. Trogoniformes

  • Bill short and stout with bristles at base.
  • Plumage brilliant green.
    Example :- Trogons (Trogon alegans), Pharomacru

Order 20. Coraciiformes

  • 3rd and 4th toes fused at base.
  • Bill strong.
    Example :- King fishers, Hornbills. Megaceryle, Merops.

Order 21. Piciformes

  • Bill stout owl-like.
  • Dig insect and larvae out of wood.
    Example :- Woodpeckers, Facamars, Puffbirds, Barbets, Honey guide and Toucans. Upupa epops, Picus.

Order 22. Passeriformes

  • Perching birds. Toes 3 in front, 1 behind.
  • Includes great majority of all known birds.
    Example :- Crows, Homed Larks, Swallows, Gous, Sparrows, Finches, Starlings, Pipits, Blackbirds, Wood warblers, Tenagers, Wax-wings and Kinglets. Passer domesticus, Molpestes, Kittacinela, Acridotheres, Corvus, Motacilla, Hirundo, Ploceus and Urolovcha.


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