Acc Biology        Notes        Homework          Home  Ch. 44 Birds

Birds:

	Well adapted to marine, freshwater, & terrestrial habitats
	Bodies adapted for flight
	Endothermic - body temperature controlled by metabolism

Evolution:

• Evolved from reptiles
• Few fossils due to lack of preservation of feathers or thin, hollow bones
• Archaeopteryx:
  1. Possible link between birds & reptiles
  2. Lived during Jurassic period
  3. Large skull with reptile like teeth
  4. Bones not hollow
  5. Claws on forelimbs
  6. Long tail
  7. Strong legs & rounded wings for gliding
  8. Feathers
  9. Furculum - fused collarbone or wishbone

Archaeopteryx Fossil

• Hesperonis:
  1. Bird fossils from Cretaceous period
  2. Large, flightless bird
  3. Had teeth like reptiles

Hesperonis

• Ichthyornis:
  1. Smaller, tern like bird
  2. Lived during Cretaceous period
  3. Had large flight wings

Characteristics of Birds:

• Body covered with feathers made of protein called keratin

• Thin, hollow bones

• Some bones fused for extra strength

• Forelimbs modified into wings for  flight

• Two hind limbs with claws to support upright body

• Scales on legs

• Toothless, horny beak

• Additional air sacs  with lungs for more oxygen

• Endotherms (40 to 41 degrees Celsius body temperature)

• Four chambered heart with single, right aortic arch

• Amniote egg with calcium carbonate shell

• Oviparity with both parents often caring for eggs

• Eggs usually incubated within a nest

Feathers:

• Modified scales

• Function to provide lift for flight & help conserve body heat

• Five kinds of feathers ----- down, contour, flight, filoplume, & bristles

Types of Feathers

• Down feathers:
  1. Soft & fluffy
  2. Cover the body of nestlings
  3. Provide an undercoat insulating adult birds

• Contour Feathers:
  1. Give streamline shape to body
  2. Provide coloration to adult birds
  3. Give additional insulation to body

• Flight Feathers:
  1. Specialized contour feathers
  2. Found on wings & tail

• Filoplumes:
  1. Called pin feathers
  2. Hairlike feathers under contour feathers on body

Parts of a feather:

• Develop from tiny pits in the skin called follicles

• Shaft emerges from the follicle

• Two vanes develop on either side of shaft

• Barbs branch off of each vane & have projections called barbules

• Barbules have microscopic hooks to hold barbules together

Parts of a Flight Feather

Microscopic Hooks on Barbules

• Birds preen their feathers to clean them & coat them with oil

• Preen glands - oil glands located at the base of the tail

• Birds shed or molt feathers periodically:
  1. Molting usually in late summer between breeding & migration
  2. Flight feathers replaced
  3. Some birds molt before courtship

Beaks and Feet:

• Adapted to habitat & feeding

• Hawks & eagles have hooked beaks & talons for tearing meat

• Swifts have tiny beaks that open wide to catch insects in midair

• Flightless birds like ostriches have legs & feet modified for running & walking

• Penguins have wings modified into flippers for swimming

• Ducks & geese with webbed feet

Running Legs of Ostrich	Webbed Feet on Duck

• Legs of some birds such as herons &  egrets turn vivid colors to attract mates; caused by hormones

Skeleton and Muscles:

• Pelvic & pectoral girdles fused for strength

• Bones thin & hollow so bird lighter

Hollow Bones

• Furculum or wishbone is a fused collarbone that stabilizes bird in flight

• Lighter beak replaces heavy teeth & jaws

• Lower vertebrae fused so no heavy ligaments needed

• Enlarged eye sockets reduce skull weight

• Keeled sternum for attachment of large flight muscles

• Pygostyle - terminal vertebrae support tail & aids in flight (lift, steering, & braking)

• Two digits in forelimbs lost & other three digits fused to form wings

• Wings shaped like air foils (thicker in front & tapering to back) so air moves faster on top causing lift

• Powerful muscles make up 50% of body weight

• each wing movement uses different set of muscles

• Flight muscles called pectorals & are attached to wing & keeled sternum

• When large pectorals contract, wings move down

• When large pectorals relax & small pectorals contract, wings move upward

Body Temperature:

• Metabolism generates body heat (endothermic)

• Enables birds to survive in warm & cold environments

• Rapid breathing & increased air sacs in lungs bring in more oxygen

Air Sacs in Bird Lungs

• Ingest large amounts of food for energy

• Fluff out feathers to trap air for insulation

• Aquatic birds have thin layer of fat for insulation

Digestive System:

• Fast & efficient digestion (mouse digested in 3 hours)

• No chewing

• Crop for temporary food storage

• Two part stomach --- proventriculus & gizzard

• Proventriculus is 1st chamber where digestive juices added

• Gizzard is 2nd part for crushing food

• Small stones & gravel eaten by birds aids grinding in gizzard

• Pyloric sphincter valve at lower end of gizzard controls food movement into intestines

• Duodenum - beginning of small intestine where bile (digests fats) & pancreatic juice are added & digested food is absorbed

Excretory System:

• Paired kidneys filter nitrogen wastes (uric acid) from blood

• No urinary bladder to store liquid wastes

• Uric acid travels down ureters to cloaca where intestinal wastes & reproductive products added

• Uric acid secreted in white, semi solid mass

• Shorebirds have salt secreting glands above the eyes & secrete excess salt through their nostrils

Respiratory System:

• Fly at high altitudes where there is less oxygen so need efficient respiratory system

• High metabolic rate requires large amount of oxygen

• Nine air sacs associated with lungs increase oxygen level & decrease density

• Air sacs connected to air spaces in hollow bones

• One way flow of air in lungs & air sacs so more oxygen is removed

• Air pathway:
  air enters body through nostrils on beak  trachea (windpipe) syrinx (voice box) 2 primary bronchi 75% of air into two posterior air sacs and 25% of air into lungs air from lungs into other seven air sacs

• When carbon dioxide exhaled, oxygen from posterior air sacs moves into lungs to always keep fresh oxygen supply

Circulatory System:

• Four chambered heart

• Right side of heart pumps deoxygenated blood from body cells to lungs

• Left side of heart receives oxygenated blood from lungs & pumps it to the body cells

• Single aortic arch

• Rapid heartbeat (hummingbird 600X/minute & chickadee 1000X/minute)

• Less active birds such as ostrich have slower heart rates (70X/minute)

Nervous System:

• Large brains relative to size of bird

• Most highly developed brain areas control flight

• Cerebellum coordinates movement

• Cerebrum controls navigation, mating, nest building, & care of young

• Optic lobes receive & interpret visual stimuli

• Keen vision

• Have color vision for locating food

• Large eyes located on side of head for wide field of vision in most birds

• Some birds such as owls with eyes on front of head for binocular vision (depth perception)

• No external ears, but have feathers around ear openings to direct sounds into ear canals

• Tympanic membrane or eardrum for picking up sound vibrations

• Semicircular canals in inner ear regulate balance

• Poorly developed sense of smell except in ducks & flightless birds

• Sense of taste helps avoid bitter tasting or toxic foods

Reproductive System:

• Testes in males produces sperm that travels by the vas deferens to cloaca

• Females have single ovary that makes eggs

• Eggs are fertilized in the oviducts

• Shell added by shell gland & then egg moves into 

• In mating, male presses cloaca to female to transfer sperm (internal fertilization)

• Lay an amniote egg:
  1. Embryo suspended in fluid called albumen (white of egg)
  2. Chalaza - rope like strands suspending embryo in albumen
  3. Chorion is membrane inside of shell
  4. Yolk is stored food surrounded by yolk sac

Bird Egg

Incubation & development of Egg:

• Eggs incubated by one or both parents 

• Brood patch - thickened, featherless patch of skin on abdomen of bird used to warm eggs

• Membranes grow out of embryo's digestive tract & surround yolk

• Membranes make digestive enzymes to dissolve proteins & lipids in yolk

• Yolk sac has blood vessels to carry food to embryo

•  Wastes from embryo collect in membrane called allantois

• Chorion membrane lines the shell & allows gas exchange

• Young birds may be precocial or altricial

• Precocial young:
  1. Have longer incubations
  2. More eggs laid
  3. Active as soon as hatch
  4. Nestlings can swim, walk, & feed themselves
  5. Need some parental care
  6. Includes ducks, geese, & swans

• Altricial young:
  1.Lay fewer eggs
  2. Hatch quickly
  3. Hatchlings are blind, naked, & helpless
  4. Depend on parents for warmth & food for several weeks
  5. Includes songbirds, woodpeckers, hawks, pigeons, doves, raptors

Behavior:

• Longer parental care allows more complex learning (courtship, nesting, migration, etc.)

• Territoriality allows males to establish & defend breeding areas

• Courtship behaviors are used by males to attract mates:
  1. Brightly colored feathers
  2. Flight displays
  3. Songs

Male Scarlet Tanager Breeding Plumage

• Nest building holds eggs, conceals & shelters young birds, may help attract mates

• Nests are built in sheltered, well-hidden spots in trees, on the ground, etc. & are made of twigs, mud, grass, feathers...

• Migration to new areas is triggered by dropping temperatures & dwindling food supplies

• Birds use migration clues including:
  1. Position of sun & stars
  2. Topographical landmarks
  3. Magnetic clues
  4.Air pressure changes
  5. Low frequency sounds

 Classification:

• Class Aves

• 27 orders

• Gaviiformes - loons

• Pelecaniformes - pelicans & cormorants

• Ciconiiformes - wading birds like ibises & herons

• Anseriformes - ducks, geese, & swans

• Falconiformes - falcons, eagles, hawks, vultures

• Galliformes - turkey, quail, pheasants

• Gruiformes - cranes, coots, & rails

• Charadriiformes - snipes, sandpipers, gulls, terns

• Columbiformes - pigeons & doves

• Psittaciformes - parrots, parakeets, & macaws

• Cucluiformes - cuckoos & roadrunners

• Strigiformes - owls

• Caprimulgiformes - whippoorwill & nighthawk

• Apodiformes - hummingbird & swifts

• Coraciiformes - kingfishers

• Piciformes - woodpeckers, sapsuckers, & flickers

• Passeriformes - perching birds like robins, cardinals, blue jays

Pygmy Owl Brown Pelican Macaw Female Cardinal Food & Habitat Adaptations: Anseriformes (ducks, geese, & swans) have webbed feet for swimming & flattened bills; young are precocial but need some parental care Strigiformes (owls) have sharp, hooked beaks & talons (claws) for meat eating, keen hearing & eyesight, & forward facing eyes Apodiformes (hummingbirds) are small, fast-flying birds with tiny feet & long tongues for drinking nectar; found only in western hemisphere Psittaciformes (parrots, cockatoos, parakeets...) have a strong, hooked beak for seed opening & two forward & two rear facing toes for perching & climbing Piciformes (woodpeckers, toucans, & flickers) have two rear facing toes for dwelling in tree cavities & sharp, chisel like bills for drilling into trees Falconiformes or raptors ( hawks, eagles, vultures) have hooked beaks & talons & keen vision for seeing prey Passeriformes or songbirds (blue jays, cardinals, sparrows, robins ...) have enlarged rear facing toe to grip branches, a syrinx or voice box in males to produce songs, & a variety of beak shapes to feed on seeds, nectar, fruits, & insects; known as passerines or perching birds Columbiformes (pigeons & doves) have small heads & bills, a crop that makes "pigeon's milk" for feeding young, short incubation period (2 weeks)  Ciconiiformes (herons, ibises, & egrets) have long legs for wading & sharp pointed bills for piercing frogs & fish Galliformes (turkeys, quail, pheasants, & chickens)  have plump bodies with limited flying &a large gizzard for grinding grains Sphenisciformes (penguins) have wings modified into flippers, an extra layer of body fat for insulation, & webbed feet for swimming Struthioniformes (ostrich) are the largest birds that can't fly but have long legs with only two toes adapted for fast running

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