BirdsBirds

Evolution and Evolution and ClassificationClassification

Birds are Vertebrates Birds are Vertebrates of the Class Avesof the Class Aves

The evolution of The evolution of warm-blooded, has warm-blooded, has enabled birds to enabled birds to survive in virtually survive in virtually every known every known environmentenvironment

Origin and Early EvolutionOrigin and Early Evolution

Evidence from fossils Evidence from fossils and from studies of and from studies of comparative comparative anatomy indicates anatomy indicates that birds evolved that birds evolved from reptilesfrom reptiles

Their features and Their features and their fragile hollow their fragile hollow bones do not bones do not preserve well.preserve well.

ArchaeopteryxArchaeopteryx The fossil genus The fossil genus

Archaeopteryx link Archaeopteryx link between reptiles and between reptiles and birds, these mammals birds, these mammals possessed characters of possessed characters of both reptiles and birds.both reptiles and birds.

Like reptiles it had a large Like reptiles it had a large skull with teeth, bones skull with teeth, bones that weren’t hollow, claws that weren’t hollow, claws on its forelimbs, and a on its forelimbs, and a long tail.long tail.

Its strong legs and Its strong legs and rounded wings indicated rounded wings indicated that it glided rather than that it glided rather than flew flew

ArchaeopteryxArchaeopteryx In contrast, the presence In contrast, the presence

of feathers and of a of feathers and of a furculum, the fused furculum, the fused collarbones commonly collarbones commonly called the wishbone, called the wishbone, suggest that suggest that Archaeopteryx was Archaeopteryx was birdlike birdlike

After Archaeopteryx the After Archaeopteryx the next bird fossil dates next bird fossil dates from about 90 million from about 90 million years ago, in the years ago, in the Cretaceous period. Cretaceous period.

HesperornisHesperornis Hesperornis, a large, Hesperornis, a large,

flightless, driving bird, flightless, driving bird, probably resembled the probably resembled the modern loon but had modern loon but had reptilian teeth.reptilian teeth.

A smaller ternlike bird A smaller ternlike bird called Ichthyornis had called Ichthyornis had large wings, indicating large wings, indicating that it may have been a that it may have been a strong flier.strong flier.

The development of The development of sustained flight may have sustained flight may have been enabled birds to been enabled birds to colonize new areas during colonize new areas during the Cretaceous.the Cretaceous.

ClassificationClassification Most taxonomist Most taxonomist

classify the nearly classify the nearly 9,000 species of Class 9,000 species of Class Aves into 27 ordersAves into 27 orders

To classify birds into To classify birds into orders and families orders and families taxonomists most taxonomists most often use often use morphological morphological evidence from beaks, evidence from beaks, feet, plumage, bone feet, plumage, bone structure, and structure, and musculature.musculature.

Characteristics of BirdsCharacteristics of Birds The following characteristics distinguish birds from other The following characteristics distinguish birds from other

Vertebrates: Vertebrates: Body covered with feathersBody covered with feathers Bones are thin and hollowBones are thin and hollow The forelimb function on wings I used for flight not graspingThe forelimb function on wings I used for flight not grasping The two hind limbs, with clawed toes support bodyThe two hind limbs, with clawed toes support body A toothless, horny break in presentA toothless, horny break in present Body temperatures is generated and regulated internallyBody temperatures is generated and regulated internally The 4-chambered heart has a single right aortic archThe 4-chambered heart has a single right aortic arch Amniote eggs are encased in hard, calcium-containing shells.Amniote eggs are encased in hard, calcium-containing shells. Most species eggs are incubated in a nest.Most species eggs are incubated in a nest.

External CharacteristicsExternal Characteristics Soft, fluffy down feathers Soft, fluffy down feathers

cover body of nestling birds cover body of nestling birds and provide and insulating and provide and insulating undercoat for adults.undercoat for adults.

Contour feathers give adult Contour feathers give adult birds their streamlined birds their streamlined shaped and provide shaped and provide coloration and additional coloration and additional insulation insulation

Flight feathers are Flight feathers are specialized contour feathers specialized contour feathers on the wings and tailson the wings and tails

Hairlike Filoplumes, or Hairlike Filoplumes, or pinfeathers, and dust pinfeathers, and dust filtering bristles near filtering bristles near nostrilsnostrils

Feathers ContinuedFeathers Continued Feathers develop from thing pits in the skin Feathers develop from thing pits in the skin

called folliclescalled follicles At maturity each vane has many branches At maturity each vane has many branches

called barbules that are equipped with called barbules that are equipped with microscopic hooks.microscopic hooks.

In the process called preen gland located at In the process called preen gland located at the base of the tail.the base of the tail.

The major molt, during which the birds The major molt, during which the birds replaces its flight feathers, occurs in the replaces its flight feathers, occurs in the late summer between breeding and late summer between breeding and migration.migration.

Beaks and feetBeaks and feet Hawks and eagles have Hawks and eagles have

powerful break and powerful break and clawed talons that help clawed talons that help them capture and then them capture and then rip their prey.rip their prey.

Swifts have a tiny Swifts have a tiny breaks that opens wide breaks that opens wide like a catcher’s mitt to like a catcher’s mitt to share insects in midair.share insects in midair.

The feet of flightless The feet of flightless birds, on the other birds, on the other hand are modified for hand are modified for walking and runningwalking and running

Skeletons and MusclesSkeletons and Muscles Combine lightness and Combine lightness and

strengthstrength Bones are thin and HallowBones are thin and Hallow The fused bones of the The fused bones of the

trunk and hip vertebras trunk and hip vertebras and the pectoral and and the pectoral and pelvic girdlespelvic girdles

Fused bones form a sturdy Fused bones form a sturdy frame that anchors the frame that anchors the powerful breast muscles powerful breast muscles during flight and supports during flight and supports the muscles when a bird is the muscles when a bird is walking or at rest.walking or at rest.

SkeletonSkeleton

The sternum supports the large The sternum supports the large breast musclesbreast muscles

The humerus, ulna, and radius, The humerus, ulna, and radius, along with the pectoral girdle and along with the pectoral girdle and the sternum, support the wing.the sternum, support the wing.

The pygostyle, the terminal The pygostyle, the terminal vertebra of the spine, support the vertebra of the spine, support the tail feathers, which also play an tail feathers, which also play an important role.important role.

EndothermyEndothermy

Generate and regulate body heat Generate and regulate body heat internallyinternally

Enables birds to inhabit both cold Enables birds to inhabit both cold and hot climateand hot climate

Body temperature ranges from 40- Body temperature ranges from 40- 46 degrees Celsius. 46 degrees Celsius.

To help conserve body heat, birds To help conserve body heat, birds fluff out there feathers to insulation.fluff out there feathers to insulation.

Digestive and Excretory Digestive and Excretory systemsystem

Food passes from the Food passes from the mouth cavity straight to mouth cavity straight to the esophagus.the esophagus.

Enlargement of the Enlargement of the esophagus called the esophagus called the crop stores and crop stores and moistens food.moistens food.

In the first chamber, The In the first chamber, The proventriculus, gastric proventriculus, gastric fluids begin fluids begin breaking down the food.breaking down the food.

Then passes through the Then passes through the gizzard, a muscular gizzard, a muscular organ that kneads andorgan that kneads and crushes the foodcrushes the food

Excretory SystemExcretory System

The avion excretory system is also The avion excretory system is also efficient and light weight efficient and light weight

The two kidneys filter a nitrogenous The two kidneys filter a nitrogenous waste called uric acid from the bloodwaste called uric acid from the blood

highly concentrated uric acid travels highly concentrated uric acid travels by ducts called ureters to the cloaca, by ducts called ureters to the cloaca, where along with undigested matter where along with undigested matter from the intestines, it is excreted in a from the intestines, it is excreted in a semisolid, usually white masssemisolid, usually white mass

Respiratory SystemRespiratory System Air enters through paired Air enters through paired

nostrils at base of nostrils at base of beakbeakDown trachea past Down trachea past syrinx, or song boxsyrinx, or song boxenters enters two primary bronchiitwo primary bronchiito to lungslungs75% bypasses the 75% bypasses the lungs and flows directly to lungs and flows directly to posterior to sacsposterior to sacssacs sacs connect with air spaces in connect with air spaces in bones, filling the hollow bones, filling the hollow bones with airbones with air

When bird exhales the When bird exhales the carbon dioxide-rich air from carbon dioxide-rich air from the lungs, oxygen rich air is the lungs, oxygen rich air is forced out of the posterior forced out of the posterior air sacs into lungs via small air sacs into lungs via small air tubesair tubes

Circulatory SystemCirculatory System 4 chambered heart4 chambered heart Right and left sides completely separatedRight and left sides completely separated Right side receives deoxygenated blood from Right side receives deoxygenated blood from

the body and pumps it to the lungsthe body and pumps it to the lungs Left side receives deoxygenated blood from Left side receives deoxygenated blood from

the lungs and pumps it to the rest of the the lungs and pumps it to the rest of the bodybody

Has a single aortic archHas a single aortic arch Most birds have a rapid heart beat compared Most birds have a rapid heart beat compared

to other vertebrates-Hummingbird-600 times to other vertebrates-Hummingbird-600 times a minutea minute

Nervous SystemNervous System Birds have a large brains, relative to their sizeBirds have a large brains, relative to their size Cerebellum coordinates movementCerebellum coordinates movement Cerebrum controls complex behavior patterns Cerebrum controls complex behavior patterns

such as navigation, mating, and nest buildingsuch as navigation, mating, and nest building Optic lobe receives and interpret visual stimuli Optic lobe receives and interpret visual stimuli Keen vision is necessary for taking off, Keen vision is necessary for taking off,

landing, spotting landmarks, hunting and landing, spotting landmarks, hunting and feedingfeeding

Have good color visionHave good color vision Birds large eyes are located near the sides of Birds large eyes are located near the sides of

its head, giving a bird a wide field of visionits head, giving a bird a wide field of vision

Nervous systemNervous system Birds large eyes are located near the sides of its Birds large eyes are located near the sides of its

head, giving a bird a wide field of visionhead, giving a bird a wide field of vision Birds with eyes near the front of the head have Birds with eyes near the front of the head have

better binocular visionbetter binocular vision Hearing important to nocturnal species that rely Hearing important to nocturnal species that rely

on sounds to help them locate preyon sounds to help them locate prey Birds lack internal ears-ear canal leads to a Birds lack internal ears-ear canal leads to a

tympanic membrane, called an eardrumtympanic membrane, called an eardrum Sense of smell is poorly developed except in Sense of smell is poorly developed except in

ducks and flightless birdsducks and flightless birds Sense of taste helps birds avoid bitter-tasting or Sense of taste helps birds avoid bitter-tasting or

toxic foodstoxic foods

Reproductive System Reproductive System Male bird sperm is produced Male bird sperm is produced

in two testes that lie in two testes that lie beneath the kidneysbeneath the kidneys

Sperm passes through small Sperm passes through small tubes called Vasa defrentia tubes called Vasa defrentia into the males cloacainto the males cloaca

During mating the male During mating the male presses his cloaca to the presses his cloaca to the females and releases spermfemales and releases sperm

Females single ovary Females single ovary releases eggs into a long, releases eggs into a long, funnel-shaped oviduct funnel-shaped oviduct where they are ferilized by where they are ferilized by spermsperm

Reproductive SystemReproductive System Reproductive System Cont.Reproductive System Cont. Fertilized eggs move down the oviduct, where they Fertilized eggs move down the oviduct, where they

receive protective covering and a shellreceive protective covering and a shell Unfertilized egg consists of a nucleus, cytoplasm, Unfertilized egg consists of a nucleus, cytoplasm,

and a yokeand a yoke When fertilized, the embryo is suspended in When fertilized, the embryo is suspended in

albumen, the egg whitealbumen, the egg white The liquid medium is supported by ropelike strands The liquid medium is supported by ropelike strands

of material called chalaza that are attached to the of material called chalaza that are attached to the shell membraneshell membrane

Female has a shell gland that secretes a protective Female has a shell gland that secretes a protective calcium carbonate shell to surround the eggcalcium carbonate shell to surround the egg

Development and Development and Behavior Behavior

Incubation and Incubation and DevelopmentDevelopment

A female bird usually lays A female bird usually lays eggs in the nest. One or eggs in the nest. One or both parents will incubate both parents will incubate or warm the eggs by or warm the eggs by sitting on them.sitting on them.

The cover them with a The cover them with a thick, featherless patch of thick, featherless patch of skin on their abdomen skin on their abdomen called a brood patch.called a brood patch.

In penguins the male In penguins the male emperor heats the egg by emperor heats the egg by placing it on his webbed placing it on his webbed feet and enfolding it with feet and enfolding it with his warm abdomen.his warm abdomen.

Incubation and Incubation and DevelopmentDevelopment

Embryo development begins Embryo development begins when the zygote forms a plate of when the zygote forms a plate of cells on the surface of the yolk.cells on the surface of the yolk.

This plate begins to form the This plate begins to form the tissues and organstissues and organs

The membrane produces The membrane produces digestive enzymes that dissolve digestive enzymes that dissolve proteins and lipids in the yolk.proteins and lipids in the yolk.

Blood vessels in the yolk sac Blood vessels in the yolk sac membrane carry the nutrients to membrane carry the nutrients to the embryo.the embryo.

When hatching begins the When hatching begins the embryo makes a star-shaped embryo makes a star-shaped crack in the shell with a scalelike crack in the shell with a scalelike egg tooth.egg tooth.

The chick presses and scrapes The chick presses and scrapes the shell until the crack widens the shell until the crack widens enough for the chick to emerge.enough for the chick to emerge.

The egg tooth, falls off soon after The egg tooth, falls off soon after the chick hatches.the chick hatches.

Incubation and Incubation and DevelopmentDevelopment

Bird have two contrasting Bird have two contrasting methods for rearing young.methods for rearing young.

Those that lay many eggs and Those that lay many eggs and incubate them for long incubate them for long periods hatch precocial periods hatch precocial young.young.

These birds are active as soon These birds are active as soon as they hatch, they can walk, as they hatch, they can walk, swim, and feed themselves. swim, and feed themselves. For examples ducks and quail.For examples ducks and quail.

Birds that lay only a few eggs Birds that lay only a few eggs and hatch quickly produce and hatch quickly produce altrical young.altrical young.

They depend on both parents They depend on both parents for several weeks. For ex. for several weeks. For ex. Woodpeckers, hawks, pigeons Woodpeckers, hawks, pigeons parrots.parrots.

BehaviorBehavior The long periods of parental The long periods of parental

care may enable birds to care may enable birds to learn such complex learn such complex behaviors as courtship, behaviors as courtship, nesting, and migration.nesting, and migration.

Young birds need protection Young birds need protection until they develop the until they develop the strength to fly and obtain strength to fly and obtain foodfood

Territoriality and CourtshipTerritoriality and Courtship During the breeding season During the breeding season

many male birds establish an many male birds establish an area that they defend against area that they defend against other males of their species, a other males of their species, a behavior called territoriality.behavior called territoriality.

The male then attempts to The male then attempts to attract a female to share this attract a female to share this territory.territory.

Once a territory is established Once a territory is established most birds engage in a period most birds engage in a period of courtship, behavior that is of courtship, behavior that is designed to attract a mate.designed to attract a mate.

Many males attract females by Many males attract females by means of their brightly colored means of their brightly colored feathers.feathers.

Some males combine song Some males combine song with flight displays.with flight displays.

Nest BuildingNest Building Nests hold eggs, conceal Nests hold eggs, conceal

young birds from predators, young birds from predators, provide shelter from the provide shelter from the elements, and sometimes elements, and sometimes even serve to attract a mate.even serve to attract a mate.

Most birds build nests in Most birds build nests in sheltered, well-hidden spots- sheltered, well-hidden spots- from holes in the ground to from holes in the ground to treetops.treetops.

As a further adaptation to As a further adaptation to their environment, birds their environment, birds construct their nests of construct their nests of almost any material almost any material available.available.

Twigs, grasses, feathers, and Twigs, grasses, feathers, and mud are the most common mud are the most common materials used.materials used.

MigrationMigration When temperatures drop and the When temperatures drop and the

food supply dwindles, these birds food supply dwindles, these birds migrate to warmer climates.migrate to warmer climates.

Birds rely on a variety of cues to Birds rely on a variety of cues to help them navigate.help them navigate.

Some species monitor the Some species monitor the position of the stars or the sun.position of the stars or the sun.

Others rely on topographical Others rely on topographical landmarks, such as mountains.landmarks, such as mountains.

Magnetic cues, changes in air Magnetic cues, changes in air pressure, and low –frequency pressure, and low –frequency sounds may also provide sounds may also provide information to migrating birds.information to migrating birds.

The ability of birds to read these The ability of birds to read these cues, along with their many cues, along with their many adaptations for flight, enables adaptations for flight, enables them to migrate to and inhibit them to migrate to and inhibit virtually any environment.virtually any environment.