Aves: General Characters and Classification
GENERAL CHARACTERS:
1. Birds are warm-blooded vertebrates with an exoskeleton d of feathers.
2. The fore-limbs are modified into wings each bearing three clawless digits and provided with feathers for flight.
3. The hind-limbs are adapted for walking, perching or swimming and bearing four toes. 100 bab
4. No skin gland except the oil glands on the tail. alam.
5. The bones, forming the skeleton, are spongy, light in weight containing air cavities.
6. Skull is monocondylie, having single rounded occipital condyle dation.
7. The lower jaw is composed originally of five or six bones.
8. Modern birds have no teeth. A horny beak is present.
9. The cervical and free thoracic vertebrae are usually heterocoelous but may be procoelous or amphicoelous.
10. The sacral vertebrae are fused with the lumbar and with fewer or more of the posterior thoracic and anterior caudal to form a synsacrum.
11. The posterior caudal vertebrae are usually fused to form a pygostyle.
12. Vertebral ribs are double headed, provided with uncinate process.
13. The sternum is broad, usually with a longitudinal ventral keel for the attachment of flight muscles.
14. The coracoid is usually more or less pillar-like, the scapula is sabre-shaped.
15. The clavicles and interclavicle unite to form a V-sianped furcula.
16. Distal carpals and metacarpals are united to form a carpo-metacarpus.
17. Proximal tarsals are fused with the tibia to form a tibio. tarsus and metatarsals with the distal tarsals to form the tarso- metatarsus.
18. In the leg, the ankle joint is inter-tarsal.
19. The gullet is dilated into a crop. Stomach is divided into a glandular proventriculus and a muscular gizzard. Cloaca is three chambered.
20. Lungs are spongy and non-distensible. Air sacs are present and some of them communicate with air cavities in the bones.
21. The voice is produced by the syrinx situated near the junction of the traches with the bronchii.
22. Tyrinx is without vocal cords.
23. The heart is four chambered. Only right aortic arch is present in the adult.
24. R. B. C. are oval, nucleated and biconvex.
25. Renal portal system is vestigial.
26- Kidneys are metanephric, three lobed and ureters open into the cloaca.
27. The cerebral hemispheres, and cerebellum are large and the optic lobes are displaced laterally.
28. Sexes are separate and sexual dimorphism is well marked.
29. The left ovary alone is present. The right ovary is more or less completely atrophied.
30. Fertilization is internal.
31. Oviparous. Large ovum containing much yolk invested with albumen.
32. The embryo has an amnion, an allantois and a large yolk sac. 33. Parental care is highly developed.
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CLASSIFICATION:
The classification is adopted from Storer and Usinger (1957):
Subclass :I- ARCHAEORNITHES
1. Extinct Jurassic birds of Mesozoic age.
2. Tail long with more than 13 caudal vertebrae bearing ret-rices arranged in two lateral rows.
3. Pygostyle was absent.
4. Vertebrae were amphicoelous.
5. Three fingers and metacarpals were free, each with a claw.
6. Teeth embedded in sockets were present in both jaws.
Examples: Archaeopteryx, Archaeornis.
Subclass: II-NEORNITHES
1. Living as well as extinct birds.
2. Tail is usually short, ends in a pygostyle.
3. The retrices are arranged in a semicircle around the pygo-style.
4. Teeth are absent except in few forms.
5. The metacarpals are fused with the distal carpals to form a carpo-metacarpus.
6. Except in one case, not more than two digits of the hand bear claws.
7. Claws are absent in the fore-limbs.
8. The sternum is well developed and usually provided with a keel or carina.
9. Vertebrae are heterocoelous in living forms.
10. Caudal vertebrae are 13 or less.
Superorder: I-ODONTOGNATHAE
1. Extinct cretaceous birds.
2. Teeth present in furrows on jaws.
Examples: Hesperornis, Ichthyornis
Superorder: II PALAEOGNATHAE
1. Mostly flightless walking or running birds.
2. Wings are reduced or absent.
3. Teeth are absent.
4. Tail vertebrae are free.
5. Coracoid and scapula are small and fused at an obtuse angle.
6. Sternum devoid of keel or carina.
Order 1. Struthioformes
1. Large flightless terrestrial birds.
2. Head, neck and legs feathered.
3. Feathers without aftershaft.
4. Head is comparatively small and the neck is very long and flexible.
5. The beak is short and broad.
6. Only two toes (3rd and 4th) on each foot.
7. Sternum without keel.
8. Pubic symphysis present.
9. No pygostyle.
Example: Struthio camelus (Ostrich).
Order 2. Casuariiformes
1. Large flightless terrestrial birds.
2. Head is sparsely feathered while neck and body densely feathered.
3. Feathers with aftershaft nearly equal to shaft.
4. Wings small or rudimentary.
5. Three toes with typical claws on each foot.
6. Sternum without keel.
Examples: Dromaeus (Emus), Casuarius (Cassowaries).
Order 3. Aepyornithiformes
1. Flightless, terrestrial extinct elephant birds.
2. Wings vestigial or tiny.
3. Legs powerful with 4 toes.
4. Sternum short, broad and without keel.
5. Eggs were surprisingly large.
Example: Aepyornis (Extinct).
Order 4. Dinornithiformes
1. Giant flightless, terrestrial, extinct birds.
2. Feathers with large aftershaft.
3. Wings almost absent.
4. The beaks were short.
5. Legs massive bearing 4 toes.
6. Sternum reduced and without keel.
7. Pectoral girdle completely absent.
Example: Dinorais (Moas) Extinct.
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Order 5. Apterygiformes
1. Flightless terrestrial birds.
2. Feathers fluppy hair-like without aftershafts.
3. Wings are rudimentary or degenerate.
4. The beak is long and slender with nostrils at the tip of the maxilla.
5. The eyes are small.
6. The neck and legs are comparatively short.
7. Legs bear 4 toes.
8. Sternum without keel.
9. Eggs are relatively largest of all the living birds.
10. Nocturnal, feeding on worms and insects.
Example: Apteryx (Kiwi).
Order 6. Rheiformes
1. Flightless terrestrial and swift-running birds.
2. Head, neck and thighs are feathered.
3. Feathers without aftershaft.
4. Wings are better developed.
5. Legs bear 3 toes with heavy and typical claws.
6. Sternum without keel.
Example: Rhea americana (American Ostrich).
Order 7. Tinamiformes
1. Small, terrestrial, essentially cursorial with poor power of flight.
2. Wings are short and rounded.
3. Sternum is keeled.
4. Tail feathers and pygostyle are reduced. 5. Eggs are remarkable with highly glossy shells.
6. Vegetarian.
Examples: Tinamus, Rhyncolus.
Superorder III-NEOGNATHAE
1. Molern, usually small flying birds.
2. Skull is neognathus, i.e., with short vomer and palatines extending posteriorly.
3. Teeth are entirely absent.
4. Feathers having interlocking mechanism.
5. Wings well developed.
6. Sternum with a well developed keel.
7. Tail vertebrae are 5 or 6. 8. Pygostyle present.
9. Fore limbs with metacarpals joined and fingers included in wings.
Order 1. Sphenisciformes
1. Flightless aquatic birds.
2. Feathers small scale-like covering the entire body.
3. Fore limbs (wings) are paddle-like adapted for swimming.
4. Feet webbed.
5. Metatarsus incompletely fused, 4 toes all directed forward.
6. Bones are much compressed.
7. Thick layer of fat present beneath the skin.
Example: Aptenodytes (Penguin).
Order 2. Gaviiformes
1. Legs are short and at the end of the body.
2. Tail comprises 18-20 short stiff feathers.
3. Toes are fully webbed.
4. Patella reduced.
5. Powerful in flight.
Example: Garia immer (Common loon).
Order 3. Podicipitiformes
1. Fresh water divers.
2. Legs are placed far back on the body.
3. Feet are lobed.
4. Tail comprises a tuft of down feathers.
5. Patella is large.
6. Tarsus is compressed.
Examples: Podiceps, Podilymbus.
Order 4. Procellariiformes
1. Nostrils are tubular.
2. Horny sheath of bill consisting of several plates.
3. Skull with large nasal glands.
4. Hind toe is vestigial or none.
5. Feathers compact and oily in texture.
6. Wings are long and narrow.
7. Strictly marine, nest usually on islands.
Examples: Diomedea (Albatrosse), Puffinus (Petrels).
Order 5. Pelecaniformes
1. Aquatic fish-eating and colonial nesters. 2. Nostrils are vestigial or absent.
3. Presence of a gular pouch on the throat.
4. Four toed webbed feet.
5. Beaks are long with wide gapes for catching and swallowing the struggling prey. Example: Pelecanus (Pelecan)
Order 6. Ciconiiformes
1. Long necked and long legged birds.
2. Feathers are decorative.
3. Beaks abruptly decurved at middle in flamingos.
4. Toes are without web.
5. Young born naked.
6. Food comprises fish and other aquatic animals.
Examples: Ardea (Great blue heron), Phenicopterus (Flamingo).
Order 7. Anseriformes
1. Beak or bill is broad, covered with soft cornified epidermis,
2. Margins of the beak containing many transverse ridges (lamellae). horny
3. Tongue is fleshy.
4. Legs are short and feet are webbed.
5. Tail is usually short, consisting of many feathers.
Examples: Ducks, Geese, Swans.
Order: 8. Falconiformes
1. Beak is short and curved at the tip.
2. Mandibles are sharp edged.
3. Fest usually with sharp curved claws adapted for grasping and holding the prey. 4. Diurnal and strong fliers.
Examples: Vultures, Kites, Hawks and Faloons.
Order 9. Galliformes
1. Terrestrial game birds with short and powerful flight.
2. Beak is short.
3. Feathers with aftershaft.
4. Feet usually massive adapted for scratching and running.
5. Graminivorous.
Examples: Gallus (Jungle fowl), Pavocristatus (Peacock), Coturnix (Quail), Francolinus (Grey patridge), Phasianus (Pheasants).
Order 10. Gruiformes
1. Small, medium and large-sized birds.
2. Flightless or weak fliers or strong fliers.
3. Feathers with aftershaft.
4. Legs long and beaks heavy.
Examples: Grus (Crane), Fulica atrica (Common coot), Antegna antegona (Sarus crane).
Order 11. Diatrymiformes
1. Large flightless extinct birds.
2. Wings atrophied.
3. Massive head, beak and neck.
4. Foot bears 4 toes.
Example: Diatryma (Extinct).
Order 12. Charadriiformes
1. Shore dwelling aquatic birds.
2. Fore and hind limbs are slender and enormously elongated.
3. Toes usually webbed. 4. Beaks mud probing.
5. Feathers are dense and firm.
Examples: Lobivanellus indicus (Red wattled lapwing), Hydro- phasianus chirugwe (Pheasant tailed jacana), Tringa glariola (Sand piper), Capella (Snipe), Larus (Gull), etc.
Order 13. Columbiformes
1. Skin thick and soft.
2. Beak usually short and slender.
3. Tarsus usually shorter than toes.
4. Crop large producing "pigeon milk" to feed young ones.
5. Graminivorous and frugivorous. Examples: Columba livia (Blue rock pigeon), Goura cristata (Crow- ned pigeon), Streptopelia risoria (Ring dove), Streptopelia chinensis (Spotted dove), etc.
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Order 14. Cuculiformes
1. Toes 2 in front and 2 behind, out hind toe reversible.
2. Feet not adapted for grasping.
3. Tail long and beak moderate.
4. Many cuckoos are parasitic, the female laying eggs in nest of other birds.
Examples: Cuculus canorus (Cuckoo), Budynamis scolopaceous (Koel).
Order 15. Psittaciformes
1. Feathers are green, blue, yellow or red.
2. Beak stout, narrow, sharp edged and hooked at the
3. Upper jaw is movably articulated with the skull tip.
4. Feet zygodactylus, i.e., two toes infront and two toes behind.
5. Outer toe is not reversible. Example; Psittacula eupatra (Large Indian Parrakeet), Psittacula krameri (Green parrot).
Order 16. Strigiformes
1. Head large and rounded.
2. Eyes large and directed forwards. Each in a disc of radial feathers.
3. Retina contains principally the rods. dim
4. Ear opening large, often with flap-like cover.
5. Beak short, feet with sharp claws adapted for grasping.
6. Nocturnal and predators. Examples: Bubo bubo (Great horned owl), Ketupa zeylonensis (Brown fish owl).
Order 17. Caprimulgiformes
1. Beak is small and delicate.
2. Mouth is wide and margined with long bristle-like sensory feathers.
3. Feathers are soft and lax.
4. Legs and feet small and weak, not adapted for grasping.
5. Nocturnal and insectivorous.
Example: Caprimulgus.
Order 18. Apodiformes
1. Usually small birds.
2. Legs are very short and feet very small.
3. Wings pointed.
4.Beak is small and weak or slender with long tubular tongue.
Examples: Swifts, Humming birds.
Order 19. Coliformes
1. Small passerine birds.
2. First and fourth toes are reversible.
3. Tail is very long.
4. Insectivorous and frugivorous. Colins (Mouse bird).
Order 20. Trogoniformes
1. Beak short and stout with bristles at the base.
2. Feet small and weak.
3. Feathers brilliant in colour, often green.
Example: Trojos
Order 21. Coraciformes
1. Beak strong,hal saly
2. Third and fourth toes fused at the base.
Example: King-fisher.
Order 22. Piciformes
1. Tail feathers are stiff with pointed tips.
2. Beaks stout and owl-like.
3. Protrusible tongue is roughened or with barbs at the tip.
4. Two toes in front and two or one behind, not reversible.
Examples: Dryobates (Yellow front pied woodpecker). Brachy- pter nus bengalensis (Golden beak woodpecker).
Order 23. Passeriformes
1. Toes three in front and one behind, adapted for perching.
2. Toes are adapted for cutting.
Examples: Passer domesticus (Common house sparrow), Corvus splendens (Common house crow), Acridotherus tristie (Common myna), Saxicoloides fulicata (Indian robin), Oriolus oriolus (Golden oriole). Bulbul, Swallos.
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