Wings, feathers, bird-like head, clawed digits and toothed beak

Aves | CEE Academy

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AVES / BIRDS

▢ Introduction:

Table 1: Basic Terms

Term	Meaning
Ornithology	Study of birds
Oology	Study of bird eggs
Phenology	Study of seasonal biological events e.g. bird migration timing
Origin	Birds originated near end of Jurassic period of Mesozoic era
Ancestry	Reptilian ancestry

❖ Quotes:

Table 1: Quotes on Birds

Scientist	Quote
Huxley	Birds are glorified reptiles
Young	Birds are masters of the air

▢ Archaeopteryx:

Table 1: Archaeopteryx

Feature	Point
Nature	Primitive bird
Evolutionary importance	Connecting link between reptiles and birds
Bird-like characters	Wings, feathers, bird-like head
Reptile-like characters	3 clawed digits in each wing; toothed beak
Extinction	Cretaceous period
Fossil found	Germany

▢ General Characters:

❖ Key Features:

•
Feathered bipeds
•
Air-breathing vertebrates
•
True flying vertebrates except bats
•
Warm-blooded / homoiothermous
•
Body adapted for flight

❖ Body Divisions:

Table 1: Body Divisions

Part	Feature
Head	Jaw bones prolonged into toothless beak / bill
Neck	Long + flexible
Trunk	Compact; bears limbs
Forelimbs	Modified into wings
Hindlimbs	Large; clawed toes
Tail	Short; supports tail feathers

❖ Skin:

•
Skin without glands
•
Only uropygial / preen gland present at base of tail
•
Uropygial gland secretion used for preening feathers

▢ Skeletal System:

❖ Exoskeleton:

Table 1: Exoskeleton of Birds

Component	Point
Feathers	Keratinized structures; show reptilian ancestry
Scales	Present on legs
Claws	Present on toes

❖ Feathers:

Table 1: Types of Feathers

Type	Point
Quill feathers	Flight feathers
Contour feathers	Body outline + streamlining
Filoplume feathers	Sensory / hair-like feathers
Down feathers	Insulation

Table 2: Quill Feathers

Term	Location / Meaning
Remiges	Quill feathers of wings
Rectrices / Retrices	Quill feathers of tail
Coverts	Feathers at bases of wing-quills

❖ Endoskeleton:

Table 1: Endoskeleton Features

Feature	Point
Bones	Pneumatic + hollow; no marrow
Skull	Monocondylic like reptiles
Vertebrae	Heterocoelous / saddle-shaped
Synsacrum	Fusion of posterior thoracic + lumbar + sacral + anterior caudal vertebrae
Pygostyle	Fusion of last tail vertebrae
Sternum	Large with midventral keel
Keel	Attachment site for flight muscles
Ribs	Posteriorly directed uncinate process
Furcula	V-shaped bone from fused clavicles + interclavicle

▢ Digestive System:

Table 1: Digestive System

Part	Feature / Function
Beak	Toothless jaws
Crop	Dilated oesophagus; storage + feeding
Pigeon milk	Crop secretion during breeding season
Proventriculus	Glandular stomach
Gizzard	Muscular stomach
Rectal caecae	At junction of small intestine and rectum
Cloaca	Common chamber for digestive, urinary, reproductive openings
Gall bladder	Absent in some birds e.g. pigeon

❖ Cloaca Chambers:

Table 1: Cloaca

Chamber	Position
Coprodaeum	Anterior
Urodaeum	Middle
Proctodaeum	Posterior

❖ Excretion: Uricotelic

▢ Circulatory System:

Table 1: Circulation

Feature	Point
Heart	4-chambered
Systemic arch	Only right aortic arch persists
RBCs	Minute, oval, nucleated
Renal portal system	Vestigial

▢ Respiratory System:

Table 1: Respiration

Structure	Feature
Lungs	Compact, spongy, non-distensible
Air sacs	Continuous with lungs
Syrinx	Sound box at junction of trachea and bronchi

▢ Reproductive System:

Table 1: Reproduction in Birds

Feature	Point
Sexes	Separate
Sexual dimorphism	Present in some birds e.g. parrot, peacock
Development	Oviparous
Female reproductive organ	Single functional ovary + oviduct / Müllerian duct
Parental care	Well marked

❖ Egg:

Table 1: Bird Egg

Feature	Type
Shell	Cleidoic / calcareous shell
Yolk amount	Macrolecithal / yolk-rich
Yolk distribution	Telolecithal
Cleavage	Discoidal + meroblastic
Development	Direct

▢ Nervous & Sense Organs:

Table 1: Nervous System & Sense Organs

Feature	Point
Cranial nerves	12 pairs
Eyes	Nictitating membrane present
Pecten	Found near blind spot
Cerebellum	Well developed for flight coordination

▢ Muscular System:

❖ Flight Muscles:

Table 1: Flight Muscles

Muscle	Main role
Pectoralis major	Downstroke / lowers wings
Pectoralis minor	Upstroke / raises wings
Coraco-brachialis longus	Assists wing movement
Coraco-brachialis brevis	Assists wing movement
Tensor muscles	Tension control during wing movement

▢ Flightless Birds:

❖ General Characters:

•
Powerful well-developed legs
•
Small head
•
Rudimentary wings
•
Oil glands absent in most
•
Keel absent
•
Pygostyle absent
•
Syrinx absent
•
Leg bones solid

❖ Examples:

Table 1: Flightless Birds

Bird	Important points
Ostrich	Largest living bird; polygamous; egg ≈ 1.5 kg; largest egg; male incubates eggs; easily domesticated
Penguin	Flightless aquatic bird
Kiwi	New Zealand; smallest living flightless bird; feathered head + neck; nostrils near beak apex; nocturnal + burrowing; good smell; largest egg relative to body size; oil gland present
Rhea	Pampas of South America; head + neck feathered
Tinamus	Neotropical / South America; bird continent
Emu	Flightless bird

▢ Bird Migration:

❖ Instinct:

◉ Definition: Innate fixed behaviour pattern in response to stimuli

◉ Example: Young birds returning to original breeding ground of parents

❖ Migration:

•
Initiated by photoperiod
•
Daylight affects endocrine glands
•
Compass direction determined using celestial bodies
•
Sun used during day
•
Stars used at night

▢ Some Important Birds:

Table 1: Bird Examples

Bird	Important points
Crow	Common bird of Indian towns and villages; koel lays eggs in crow nests
House sparrow	Common house bird; conical beak; small eyes; omnivorous
Parrot / Indian parrot / Tota	Grass-green plumage; short stout sharp beak; upper mandible movable; sexual dimorphism; male has rose-pink collar + black throat
Peacock / Peafowl / Mor / Mayur	Shows sexual dimorphism; ornamental tail feathers in male
Cuckoo / Koel	Lays eggs in nests of other birds
Bengal vulture	Scavenger; feeds on carrion
Dodo	Recently extinct bird from Mauritius; extinct in 17th century
Albatross	Marine bird; largest flying bird
Humming bird / Sunbird	Smallest bird; found in Cuba; about 3 cm + 2 g; can fly backwards; nectar sucking; thin pointed beak
Swift	Fastest flying bird; ≈ 60 km/h; found in Japan
Wagtail	Migratory bird of India; comes from Siberia; nests outside India
Arctic tern	Champion long-distance migrant; longest annual migration
Siberian crane	Migratory bird
Golden plover	Migratory bird
Hoopoe	Fan-shaped crest on head
Flamingo	Large bird with long neck + legs
Great Indian bustard	Elongated bird

▢ High-Yield Recall:

Table 1: Aves One-Liners

Fact	Answer
Study of birds	Ornithology
Study of bird eggs	Oology
Bird origin era	Mesozoic era
Bird origin period	Late Jurassic
Connecting link between reptiles and birds	Archaeopteryx
Archaeopteryx fossil	Germany
Birds are glorified reptiles	Huxley
Birds are masters of air	Young
Bird body covering	Feathers
Only skin gland	Uropygial / preen gland
Wing quill feathers	Remiges
Tail quill feathers	Rectrices / retrices
Bird bones	Pneumatic + hollow
Bird skull	Monocondylic
Bird vertebrae	Heterocoelous
Fused posterior vertebrae	Synsacrum
Fused tail vertebrae	Pygostyle
Flight muscle attachment	Keel of sternum
Fused clavicles	Furcula
Glandular stomach	Proventriculus
Muscular stomach	Gizzard
Bird excretion	Uricotelic
Bird heart	4-chambered
Aortic arch in birds	Right aortic arch
Bird RBC	Oval + nucleated
Sound box	Syrinx
Female bird reproductive organ	Single functional left ovary + oviduct
Bird egg	Cleidoic + macrolecithal + telolecithal
Bird cleavage	Discoidal meroblastic
Eye structure near blind spot	Pecten
Wing downstroke muscle	Pectoralis major
Wing upstroke muscle	Pectoralis minor
Largest living bird	Ostrich
Smallest living flightless bird	Kiwi
Largest flying bird	Albatross
Smallest bird	Humming bird
Bird flying backwards	Humming bird
Fastest flying bird	Swift
Longest annual migration	Arctic tern
Brood parasite	Koel / cuckoo
Recently extinct bird	Dodo

Q1.

Ornithology is the study of

Q2.

Oology deals with the study of

Q3.

Nidology is the study of

Q4.

Pterylology is the study of

Q5.

Birds originated from

Q6.

Birds originated towards the end of

Q7.

Archaeopteryx is considered as

Q8.

Archaeopteryx had

Q9.

Archaeopteryx became extinct during

Q10.

Birds are best described as

Q11.

The body of birds is divisible into

Q12.

The beak of birds is covered by a bony sheath called

Q13.

Birds are edentulous because they have

Q14.

Forelimbs of birds are modified into

Q15.

Birds are called glorified reptiles because

Q16.

The only cutaneous gland present in birds is

Q17.

The largest and most powerful flight muscle in birds is

Q18.

Bird bones are pneumatic, meaning they are

Q19.

The skull of birds is

Q20.

Vertebrae of birds are

Q21.

Synsacrum in birds is formed by fusion of

Q22.

Pygostyle in birds is formed by fusion of

Q23.

The sternum of birds is keeled mainly for

Q24.

In birds, both clavicles and a single interclavicle fuse to form

Q25.

Oesophagus of birds is dilated into crop mainly for

Q26.

During breeding season, crop of pigeon secretes

Q27.

The muscular part of bird stomach is called

Q28.

The glandular stomach of birds is called

Q29.

The junction of small intestine and rectum in birds is marked by

Q30.

The cloaca of birds is divided into

Q31.

Bursa Fabricius in birds is associated with

Q32.

Respiration in birds involves compact lungs continuous with

Q33.

Air sacs in birds mainly help in

Q34.

The sound box of birds is called

Q35.

The heart of birds is

Q36.

In adult birds, only which systemic arch persists?

Q37.

Bird erythrocytes are

Q38.

Bird kidneys are

Q39.

Urinary bladder in birds is

Q40.

Birds are mainly

Q41.

Birds have how many pairs of cranial nerves?

Q42.

Middle ear of birds contains

Q43.

Pecten in birds is found in

Q44.

Pecten is absent in

Q45.

Female birds usually have functional

Q46.

Bird eggs are

Q47.

Cleavage in birds is

Q48.

Birds are amniotes because they possess

Q49.

Exchange of food between young and parents in birds is called

Q50.

Feathers are made up of

Q51.

Quill feathers in wings are called

Q52.

Quill feathers in tail are called

Q53.

Feathers at the base of quills are called

Q54.

Filoplume and down feathers mainly help in

Q55.

Birds are

Q56.

Aerial mode of animal adaptation is known as

Q57.

Archaeornithes are characterized by

Q58.

Neornithes include

Q59.

Dodo was an extinct bird from

Q60.

The largest flying bird mentioned in the content is

Q61.

The smallest bird is

Q62.

The bird that can fly backwards is

Q63.

Beak of humming bird is adapted for

Q64.

The fastest flying bird mentioned is

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