Post on 10-Feb-2016
description
BirdsClass: Aves
Characteristics
• Well adapted to marine, freshwater, & terrestrial habitats
• Bodies adapted for flight• Endothermic - body temperature controlled by
metabolism (40 to 41 degrees Celsius body temperature) )
Evolution
• Evolved from reptiles • Few fossils due to lack of preservation of
feathers or thin, hollow bones
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
• Amniote egg with calcium carbonate shell • Oviparity with both parents often caring for
eggs • Eggs usually incubated within a nest
Feathers!!!
Feathers:
• Modified scales • Function to provide lift for flight & help
conserve body heat • Five kinds of feathers ----- down, contour,
flight, filoplume, & bristles
Down feathers:
1. Soft & fluffy2. Cover the body of nestlings3. Provide an undercoat insulating adult birds
Contour Feathers:
1. Give streamline shape to body2. Provide coloration to adult birds3. Give additional insulation to body
Contour
Flight Feathers:
1. Specialized contour feathers2. Found on wings & tail
Flight feathers
Filoplumes:
•1. Called pin feathers2. Hair like feathers under contour feathers on body
Filoplumes
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
Feathers
• 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 & migration2. Flight feathers replaced3. 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
• Legs of some birds such as herons & egrets turn vivid colors to attract mates
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
• 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• 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
• 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
Respiration
• 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 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
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• Cerebellum coordinates movement • Cerebrum controls navigation, mating, nest
building, & care of young • Optic lobes receive & interpret visual stimuli • Have color vision for locating food
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 • In mating, male presses cloaca to female to
transfer sperm (internal fertilization)
amniote egg
• 1. Embryo suspended in fluid called albumen (white of egg)2. Chalaza - rope like strands suspending embryo in albumen3. Chorion is membrane inside of shell4. Yolk is stored food surrounded by yolk sac
• Eggs incubated by one or both parents • Brood patch - thickened, featherless patch of
skin on abdomen of bird used to warm eggs
• 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 incubations2. More eggs laid3. Active as soon as hatch4. Nestlings can swim, walk, & feed themselves5. Need some parental care6. Includes ducks, geese, & swans
Altricial young:
• 1.Lay fewer eggs2. Hatch quickly3. Hatchlings are blind, naked, & helpless4. Depend on parents for warmth & food for several weeks5. 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 used by males to attract mates:1. Brightly colored feathers2. Flight displays3. Songs
Courtship
• 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...
nests
Migration
• triggered by dropping temperatures & dwindling food supplies
• Birds use migration clues including:1. Position of sun & stars2. Topographical landmarks3. Magnetic clues4.Air pressure changes5. Low frequency sounds