Class Aves: BirdsClass Aves: Birds

Characteristics of Class Characteristics of Class AvesAves

Adaptations for flight (feathers/wings)Adaptations for flight (feathers/wings) Endothermic/High metabolic rateEndothermic/High metabolic rate Vertebral column modified for flightVertebral column modified for flight Bones lightened by numerous air spacesBones lightened by numerous air spaces Horny bill/beakHorny bill/beak Lack teethLack teeth 4 chambered heart4 chambered heart Super efficient respiratory systemSuper efficient respiratory system Lay amniotic eggsLay amniotic eggs

MiscellaneousMiscellaneous Largest class of terrestrial vertebratesLargest class of terrestrial vertebrates Evolved from small carnivorous Evolved from small carnivorous

dinosaurs about 150 mya.dinosaurs about 150 mya. Oldest known bird is archaeopteryx, Oldest known bird is archaeopteryx,

which had many similarities with which had many similarities with dinosaurs (teeth, claws on wings, long dinosaurs (teeth, claws on wings, long tail)tail)

External Structures: External Structures: IntegumentaryIntegumentary

A bird’s feathers are called its plumage.A bird’s feathers are called its plumage. Feathers have 3 main purposes:Feathers have 3 main purposes:

Provide lift and aid steering during flightProvide lift and aid steering during flight Waterproofing and preventing excessive heat lossWaterproofing and preventing excessive heat loss CourtshipCourtship

Feathers are modified scales made of keratin which are Feathers are modified scales made of keratin which are molted annuallymolted annually

Feathers consist of a central shaft (rachis) and the vane Feathers consist of a central shaft (rachis) and the vane (the rest of the feather)(the rest of the feather)

The vane is made of barbs and barbules that interlock to The vane is made of barbs and barbules that interlock to provide strength and catch airprovide strength and catch air

Thin skin and scales on legs and feetThin skin and scales on legs and feet Cere – skin around the beakCere – skin around the beak

Types of FeathersTypes of Feathers Contour feathers – cover the body wings and Contour feathers – cover the body wings and

tailtail Down feathers – insulating feathersDown feathers – insulating feathers Filoplume feathers – sensory functionsFiloplume feathers – sensory functions Birds preen in order to stay clean, remove Birds preen in order to stay clean, remove

dead skin cells, and remove parasitesdead skin cells, and remove parasites An oil gland at the base of the tail provides An oil gland at the base of the tail provides

natural lubrication and waterproofing for natural lubrication and waterproofing for skin and feathersskin and feathers

The Skeleton & MusclesThe Skeleton & Muscles Lightweight, yet strong due to air sacsLightweight, yet strong due to air sacs

Flight birds have MANY mitochondria Flight birds have MANY mitochondria and produce LARGE amounts of ATP in and produce LARGE amounts of ATP in their muscles. Why might this be? their muscles. Why might this be? What about chickens and turkeys?What about chickens and turkeys?

Flight: The AirfoilFlight: The Airfoil

Nutrition & DigestionNutrition & Digestion Most birds are ALWAYS hungry! They have Most birds are ALWAYS hungry! They have

to eat a lot to keep up with the energy to eat a lot to keep up with the energy necessary for flight. They have necessary for flight. They have ridiculously high metabolisms.ridiculously high metabolisms.

A bird’s beak and tongue are indicative of A bird’s beak and tongue are indicative of its food source. For example, the beak of its food source. For example, the beak of a bald eagle if specialized for tearing a bald eagle if specialized for tearing meat off live prey. (Remember the meat off live prey. (Remember the activity.)activity.)

Nutrition & Digestion Nutrition & Digestion ContinuedContinued

Crop – stores & moistens Crop – stores & moistens food, does not digest it; food, does not digest it; it allows birds to eat it allows birds to eat even when their stomach even when their stomach is full so that food is is full so that food is constantly moving constantly moving through their body and through their body and providing energy.providing energy.

Proventriculus – stomachProventriculus – stomach Ventriculus – gizzard Ventriculus – gizzard

kneads and crushes kneads and crushes food; birds swallow food; birds swallow rocks/sand in order to rocks/sand in order to enhance the function of enhance the function of the gizzardthe gizzard

Circulatory SystemCirculatory System 4 chambered heart that is large and beats very rapidly4 chambered heart that is large and beats very rapidly Veins return blood TO the heart, arteries take blood Veins return blood TO the heart, arteries take blood

away FROM the heart to the rest of the body; away FROM the heart to the rest of the body; Pulmonary vessels carry blood to and from the lungs.Pulmonary vessels carry blood to and from the lungs.

Respiratory SystemRespiratory System Birds have a greater rate of oxygen Birds have a greater rate of oxygen

consumption than any other consumption than any other vertebrate, because they must vertebrate, because they must maintain a high metabolic rate.maintain a high metabolic rate.

Birds have air sacs that extend from Birds have air sacs that extend from lungs that constantly cycle air with lungs that constantly cycle air with every breath in and out.every breath in and out.

RespirationRespiration

ThermoregulationThermoregulation Birds are endothermic. What does Birds are endothermic. What does

this mean?this mean? When birds get hot, they don’t When birds get hot, they don’t

sweat, but rather pant like a dog.sweat, but rather pant like a dog. In order to stay warm, they will tuck In order to stay warm, they will tuck

their bill under their feathers and their bill under their feathers and possibly pull one leg, then the other, possibly pull one leg, then the other, close to their body.close to their body.

Nervous SystemNervous System Birds have big brains relative to their size. Birds have big brains relative to their size.

The bigger brains function in visual learning, The bigger brains function in visual learning, feeding, courtship, nesting, and migration.feeding, courtship, nesting, and migration.

Vision – birds see in color, have eyelids AND Vision – birds see in color, have eyelids AND a nictitating membrane. Birds that hunt a nictitating membrane. Birds that hunt prey usually have eyes that face forward. prey usually have eyes that face forward. Birds that eat insects, fruit, or seeds usually Birds that eat insects, fruit, or seeds usually have eyes on the sides of their heads. WHY?have eyes on the sides of their heads. WHY?

Smell – birds do not have a highly Smell – birds do not have a highly developed sense of smelldeveloped sense of smell

Hearing – Birds can hear EXTREMELY wellHearing – Birds can hear EXTREMELY well

ExcretionExcretion Birds have a cloaca and NO bladder.Birds have a cloaca and NO bladder. They excrete uric acid.They excrete uric acid.

Reproduction & Reproduction & DevelopmentDevelopment

All birds are oviparous – they lay eggs All birds are oviparous – they lay eggs that develop outside of the bodythat develop outside of the body

Most birds compete for mates through Most birds compete for mates through courtship behavior.courtship behavior.

Over 90% of birds are monogamous Over 90% of birds are monogamous for a season and some are for a season and some are monogamous for life.monogamous for life.

ChicksChicks Altricial birds – helpless at Altricial birds – helpless at

hatching; must be fed, hatching; must be fed, kept warm, and grow kept warm, and grow rapidly.rapidly.

Precocial birds – almost Precocial birds – almost independent at hatching; independent at hatching; usually covered with down usually covered with down and can walk, run, swim, and can walk, run, swim, and feed themselves and feed themselves almost immediately.almost immediately.

Birds that don’t fly are Birds that don’t fly are usually precocial. Why usually precocial. Why might this be?might this be?

Migration & NavigationMigration & Navigation The instinct to migrate is The instinct to migrate is

usually initiated by the usually initiated by the changes in the length of changes in the length of daylight that accompanies daylight that accompanies the change in seasons.the change in seasons.

Birds use two forms of Birds use two forms of navigation:navigation: Route-based navigation Route-based navigation

– keeping track of – keeping track of landmarkslandmarks

Location-based Location-based navigation – using the navigation – using the angle of the sun, angle of the sun, changes in air pressure, changes in air pressure, and the Earth’s magnetic and the Earth’s magnetic field to guide themfield to guide them