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

Feathers Used 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 BeforeAfter

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 Chickadee

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

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

Fly up, down, left, right, backwards and upside down Wings beat 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