Aves

Bio 2

Class Aves

• Feathers• No teeth• Flexible long neck– One occipital condyle

• Scales on legs• Bones with air spaces• Endothermic• Four chambered heart

Evolution and Classification

• Birds are Vertebrates of the Class Aves

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

Origin and Early Evolution

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

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

Caudipteryx

• Feathered dinosaur• Flightless• Transitional fossil– Dinosaur arms– Dinosaur teeth

• Only front of upper jaw

– Bird feathers

Archaeopteryx

• 147 MYA• Transitional fossil– Characteristics of

reptiles– Characteristics of birds

Archeopteryx

• Reptile characteristics– Teeth– Boney tail– Fingers with claws

• Bird characteristics– feathers

Classification

• Most taxonomist classify the nearly 9,000 species of Class Aves into 27 orders

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

Endothermic

• Warm blooded

• Ability to generate heat & maintain a constant body temperature

• Can live in hot or cold climates

• Requires more food

• Requires faster body processes to generate heat

Feathers

• Uses– Flight– Insulation– Water proofing

• Homologous to scales of reptiles• Colors from– Pigments associated with epidermal cells– Striations in barbs

• Shed continuously (except Penguins)• Accelerate at different times of year (molting)

Contour Feathers

• Hollow quill• Rachis subdivided into barbs • Barbs connected by barbules• When used in flight, called

flight feathers

Down Feathers

• No barbules• Found beneath contours• Conserve head• Abundant in waterfowl

Filoplumes

• Degenerate• Hair-like• Usually two at base of contour• Possibly sensory in function

Powder Down

• Similar to down feathers– Tips disintegrate– Produce talc-like powder– Waterproofs animal

FeathersUsed in many ways• Flight

• Regulation of body temperature (thermoregulation)

• Protection of the body

• Attraction of mates

• Identification of species

Feathers

• Modified scales

• Provide lift for flight & help conserve body heat

Types of Feathers• Contour feathers

cover the body of a bird and have a strong, hollow shaft and network of hooks.

• Down feathers are small and are located under the contour feathers to insulate the bird from the cold.

Feather Anatomy

• Rachis – stiff “backbone” of feather

• Barb – branch off of rachis

• Barbule – connect barbs

• Calamus =Quill the hollow horny barrel of a birds feather.

Contour Feathers

• Flight feathers - remiges • Tail feathers - rectrices

• Act as brakes and a rudder

• Most birds have 12 tail feathers

Contour Feathers

Contour Feather

Lacking Barbules in Owl Feathers = Quiet Flight

Preening

• A bird spends part of each day making minor repairs to tears in its feathers

• Feathers are re-zipped

Preening Zips the Feathers

Before After

Feather Growth

Down Feathers

• Soft & fluffy

• Cover the body of nestlings

• Provide an undercoat insulating adult bird

Filoplumes

• Called pin feathers

• Hairlike feathers under contour feathers on body

Wings

Flight Forces

Bernoulli’s Principle

Wing Types• Elliptical– Low aspect ration (ratio of length to average width) – Greater maneuverability

• High speed– High aspect ratio– Stay aloft at low speeds

Wing Types• Dynamic soaring– High aspect ratio

• High lift– Heavy, large bodies– High lift at low speed

Keeled Sternum and Furculum

Adaptations for Flight

• Enlarged sternum– Flight muscle

attachment

• Long neck– balance

Adaptations for Flight

• Reduce body weight– No teeth– No urinary bladder

Thermals & Air Currents

Skeleton• Strong yet light bones• Pneumatized space with cross

struts• Spaces extend to air sacs of

respiratory system• Birds not any lighter than other

mammals of same size– Distribution of weight over legs

provide lower center of gravity– Aerodynamic stability

Skeleton

• The sternum supports the large breast muscles

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

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

Skeleton• Several parts fused to

increase rigidity

• Ribs brace each other in addition to attachment to vertebrae & sternum (braces are called uncinate processes)

• Clavicles fused to a furcula (pulley bone in chickens) which flexes during flight

Muscles• Pectoralis largest– Downward beat of flight

• Surpacoracoideus raises wings

• Pectoralis connects to humerus with keeled sternum.

• Surpacoracoideus connect to coracoid bone with keeled sternum

Beaks and feet

• Hawks and eagles have powerful break and clawed talons that help them capture and then rip their prey.

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

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

Feet

• Mostly bone, scales and skin

• Keeps bird from feeling cold and heat at foot

• Perching due to special tendons

Feet

Woodpecker & Honeycreeper Tongues

Beak Adaptations

• Ripping flesh

Beak Adaptations

• Eating seeds

Beak Adaptations

• Sucking nectar from flowers

Beak Adaptations

• Drilling wood

Beak Adaptations

• Catching fish

Beak Adaptations

• Basket-like bill to hold fish caught under water

Beak Adaptations

• Filtering

Circulatory System

• 4 chambered heart• Closed system• Separation of respiratory and systemic circulations• Right aortic arch leads to dorsal aorta (left in

humans)• Larger the bird, slower the heartbeat

Circulatory System

• 4 chambered heart• Right and left sides completely separated• Right side receives deoxygenated blood from the

body and pumps it to the lungs• Left side receives oxygenated blood from the lungs

and pumps it to the rest of the body• Has a single aortic arch• Most birds have a rapid heart beat compared to

other vertebrates-Hummingbird-600 times a minute

Respiratory System

• Nine air sacs– Connect to lungs and

centers of bones– Cools the bird

• Fresh air always moving– No dead ends as in

mammals• Each wing beat moves

air– Never run out of air

Respiratory System

• 9 interconnecting air sacs paired in thorax and abdomen– Divide into extensions to bones

• Branches of bronchi don’t end in alveoli as in humans– Form parabronchi – Then into air sacs

Respiration

• Takes two passes through respiratory system for a single “breath”

Respiratory System

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

Feeding & Digestion• Diet

– Euryphagous (omnivores)– Stenophagous (select diet)

• Large appetites due to high metabolic requirements• No teeth• Gizzard for grinding (keratinized plates)• Proventriculus adds gastric juices• Crop stores food• Caeca – where small intestine joins cloaca

– Hold bacteria in herbivorous birds• Young birds have bursa of Fabricius

– Process B cells of immune system

Digestive System

• Crop– Storage

• Proventriculus– Enzymes

• Gizzard– Grind food

• Cloaca– Waste– Reproduction

Digestion – Crop & Gizzard

Excretion – Uric Acid• Uric acid

metabolic excretion

• (Saves water)• Urea• Ammonia

Excretory System

• The avion excretory system is also efficient and light weight

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

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

Nervous System

• Birds have a large brains, relative to their size

• Cerebellum coordinates movement

• Cerebrum controls complex behavior patterns such as navigation, mating, and nest building

• Optic lobe receives and interpret visual stimuli

• Have good color vision

Nervous system• Birds large eyes are located near the sides of its head, giving a

bird a wide field of vision

• Birds with eyes near the front of the head have better binocular vision

• Hearing important to nocturnal species

• Birds lack internal ears-ear canal leads to a tympanic membrane, called an eardrum

• Sense of smell is poorly

Vision

• Up to 8 times keener than human vision

• Each eye moves indendtantly

Vision• Similar to humans

• Rods & cones

Migration & Navigation

• Most have established routes• ½ of all species migrate– Most from north to south in fall and south to north in

spring• Parameters of migration– Use of different routes in fall and spring– Time to complete route– Night vs day migration (or both)– Distance of migration– Use of landmarks

Direction Finding

• Factors– Use of topographical landmarks– Flock behavior by following experienced birds– Innate sense of time– Use of earth’s magnetic field– Celestial clues (both stars and sun)• Sun-azimuth orientation (use of sun and innate sense

of time)

Migration• When temperatures drop and the

food supply dwindles, these birds migrate to warmer climates.

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

• Others rely on topographical landmarks, such as mountains.

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

Migration

• Sissor-tailed flycatchar• Migates to Central and

South America in October

• Returns in April

Migration

• Arctic tern• Migrates 25,000 miles!

Behavior

• Complex behavior– Breeding– Nesting– Courtship– Feeding, etc.

Sexual Selection

Reproduction

Reproduction

• Males with paired testes• Females often have only left

ovary and oviduct• Males typically have no penis

(waterfowl do)• Egg captured by oviduct

(infundibulum)• Yolk added, then shell• Sperm remains viable in some

species 5-6 days

Nesting & Development

• Simple and complex nests• Altricial and precocial

Development and Behavior

Incubation and Development• A female bird usually lays eggs in

the nest. One or both parents will incubate or warm the eggs by sitting on them.

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

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

Territoriality and Courtship• During the breeding season many

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

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

Nest Building• Nests hold eggs, conceal young

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

Starling Nests

Weaver Bird Nest

                                           

Brood Parasitism

Cardinal or Cowbird eggs?

Migration

Bird Brains

                                                                                                

         

Benefits of Birds to Man

• Eat insects, rodents and weeds

• Spread seeds for flowers and trees

• Food • Sport• Pets

Fastest Animal

• Peregrine falcon• Strikes prey at 180 mph

Elephant Bird

• Eleven feet tall• 1100 pounds• Largest egg ever• Extinct in late 1600’s

Giant Moa

• New Zealand• Hunted to extinction

about 1600

Bird Classification

• 28 orders• 9600 species

Order Struthioniformes

• Large flightless bird• Two toes

Order Pelecaniformes

• Gular sac

Order Ciconiiformes

• Long legs for wading• Long necks

Order Anseriformes

• Flat bill• Webbed feet

Order Falconiformes

• Hooked bill• Talons• Eagle• Hawk• Falcon

Order Passeriformes

• Perching foot• Songbirds• 5000 species• Mocking bird• Thrushes• Swallows• Magpie • Crow• Starling• Jays

Order Columbiformes

• Short neck• Short legs• Pigeons• Doves

Order Strigiformes

• Large eyes• Silent flight• Nocturnal predator• Owls

Order Apodiformes

• Small bird• Rapid wingbeat• Hummingbirds

Hummingbirds

• Fly up, down, left, right, backwards and upside down

• Wings beat 50 -200 times per second

• Heart rate =600 bpm• Eat 2/3 body weight

each day• Nectar, pollen & insects

Order Galliformes

• Chicken like• Strong beaks• Heavy feet• Chicken• Turkey• Pheasants• Quail

Order Charadriiformes

• Short bill• Strong fliers• Shorebirds• Gulls

Order Psittaciformes

• Thick tongue• Hinged and movable

upper beak• Bright colors• Parrots• Parakeets

Order Piciformes

• Two toes forward and two toes backward

• woodpeckers

Order Sphenisciformes

• Webbed feet• Wings as used for

swimming• penquins