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Birds - 1

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Class Aves Birds

Birds (class Aves) are archosaurs but

almost every feature of their reptilian

anatomy has undergone modification in

their adaptation to flight.

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Class Aves Birds

Birds are found in most every habitat

from forests to deserts, even in caves.

Some birds dive in the ocean to 45 m to

catch prey.

Birds have visited both the North & South

poles.

The bee hummingbird of Cuba weighs 1.8 gand is one of the smallest vertebrate

endotherms.

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Derived Characters of Birds

A birds most obvious adaptations for flight are

its wings and feathers.

Feathers are the feature that set birds apart

from other vertebrates.

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Derived Characters of Birds

Some other theropod dinosaurs had

feathers, but they were not capable of

supporting flight.

Insulation provides support for the idea

that some dinosaurs were endotherms.

Bright colors may have been used to attract

mates.

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Characteristics of Birds

All birds also have hindlimbs

adapted for walking,

swimming, or perching.

Foot structure in bird feetshows considerable

variation.

All have keratinized beaks.

All lay shelled amniotic

eggs.

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The Origin of Birds

Birds descended from theropods a group of small,carnivorous dinosaurs.

By 147 million years ago, feathered theropods hadevolved into birds.

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The Origin of Birds

Archaeopteryx

The oldest bird known.

Skull similar to modern birds but with thecodont

teeth. Wings with feathers were present.

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The Origin of Birds

Much of the skeleton wasthat of a theropod

dinosaur.

Long bony tail Clawed fingers

Abdominal ribs

S-shaped, mobile neck

This fossil demonstrated

the connection between

theropods & birds.

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The Origin

of Birds

Archaeopteryxarose from the

theropod lineage.

Closely related to

Dromaeosaurs. More shared

derived

characters.

Many had

feathers used

for insulation

and/or social

display.

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Living Birds

The ratites, superorder

Paleognathae, are all

flightless.

Primitive archosaurpalate.

Ostriches, emus, rheas,

kiwis, tinamous.

Flat sternum, poorly

developed pectoral

muscles.

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Living Birds

All other birds are superorder

Neognathae, having a flexible

palate.

The demands of flight have

rendered the general body

form of many flying birds

similar to one another.

Flying birds have a keeled

sternum with well developedpectoral muscles.

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Living Birds

Flightlessness hasevolved in many groupsof birds.

Penguins (use wings to

swim through water). Many fossil forms

including flightless owls,pigeons, parrots,

cranes, ducks, & auks. Usually occurs on

islands with fewpredators.

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Form & Function Feathers

Feathers are lightweight,yet tough, consisting of:

A hollow quill emergesfrom the skin.

This becomes the shaftwhich bears numerousbarbs that form a flat,webbed surface, the

vane. Each barb contains many

barbules.

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Contour feathers are vanedfeathers that cover andstreamline a birds body.

Called flight feathers if they

extend beyond the body. Down feathers are soft and

have no hooks on barbules.

Filoplume feathers are hair-like function unknown.

Powder-down feathersdisintegrate as they grow,releasing powder that aids inwaterproofing.

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Feathers are homologous to reptiles

scales.

It develops from an epidermal elevation

overlying a nourishing dermal core.

In reptiles, this elevation flattens into a

scale.

In birds, it rolls into a cylinder and sinks intothe follicle from which it will grow.

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As a feather nears

the end of its growth,

keratin is deposited

to make some of thestructures hard.

The protective sheath

surrounding the new

feather splits open,and the feather

unfurls.

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When fully grown, feathers are deadlike mammalian hair.

Birds molt to replace worn out feathers.

Usually feathers are discarded gradually toavoid bare spots.

Flight feathers & tail feathers are lost inpairs to maintain balance.

Many water birds lose all their primaryfeathers at once and are grounded duringthe molt.

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Colors in birds may be pigmentary or

structural.

Red, orange, & yellow are colored by

pigments called lipochromes.

Black, brown, & gray are produced by the

pigment melanin.

Blue is created structurally by the scatteringof shorter wavelengths of light by particles

within the feather.

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Form & Function Skeleton

A light, yet still strong skeleton is a

requirement for flight.

Bird bones are laced with air cavities.

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Birds are archosaurs, and had

ancestors with diapsid skulls.

Bird skulls are highly specialized mostly

fused into one piece.

Leg bones in birds are heavier this

helps lower the center of gravity giving

aerodynamic stability.

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Modern birds are toothless.

Instead they have a keratinized beak.

Most birds have kinetic skulls.

They have a wide gape.

Upper jaw is attached loosely increasing the

gape.

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All birds that can fly

have a large, thin

keel on their

sternum thatprovides area for the

large flight muscles

to attach.

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Food & Feeding

Early birds were carnivorous, feeding

mostly on insects.

Many birds are still insectivores.

Other foods include nectar, seeds, berries,

worms, crustaceans, molluscs, fish, frogs,

small birds & mammals.

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Food & Feeding

Some birds are generalists, feeding ona wide range of food items.

Perhaps more competition for food, but less

danger of something happening to the foodsource.

Others are specialists, only feeding onone type of food.

Less competition, more danger of losing thefood source.

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