Bird

Birds All Materials © Cmassengale

 

Birds:

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

 

Talons	Hooked Beak	Penguin Flippers

 

• 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

 

Altricial Young	Precocial Young

 

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