Chapter 42Birds
Section 2
Characteristics of Birds
Feathers• Modified scales• 2 functions: conserve body heat &
provide lift for flight• Down feathers- provide insulation • Contour feathers- give adults
streamlined shape • Flight feathers- specialized on wing &
tail
Feathers- made of keratin• Feathers develop from tiny pits in
the skin called follicles.• Shaft- emerges from the follicle &
two vanes-develop on opposite sides of the shaft
• Maturity- vane has many branches- barbs- many projects from barbs = barbules
Feathers• Preening- care for feathers- birds
rub feathers with beak and secrete oil by a preen gland- located at base of tail
• Birds molt, or shed to re-grow feathers
Skeleton and Muscles• Bones are thin and hollow
• Bones are fused so they are more rigid- provides stability during flight
• Sternum- breastbone- attachment point for flight muscles
• Pygostyle- supports tail feathers
Metabolism• Endothermic- produce body heat• Have to eat often- high energy
users• Conserve body heat- fluff up
feathers• Aquatic birds have a layer of fat
and oil on feathers to keep water from body
Digestive & Excretory System
• Esophagus crop- stores & moistens food proventriculus- acid and digestive enzymes begin breaking down food gizzard- crushes food small intestines cloaca
• Uric acid- waste--- no urine (too heavy)
Respiratory System• High metabolic rate = high oxygen
use of birds
• Air sacs- redirect air to lungs
• Efficient breathing
Circulatory System• Four-chambered heart
Nervous System & Sense Organs
• Complex brain, keen eyesight, good hearing
Reproduction • Vasa deferentia- sperm pass
through small tubes• During mating, birds press cloacas
together• Ovary released to oviduct- egg
fertilized by sperm• Egg passes from oviduct- out
cloaca
Nest Building & Parental Care• Birds lay eggs in nest---why a
nest?
• Brood patch- parents incubate eggs with a thickened, featherless patch of skin on abdomen
Nest Building & Parental Care
• Two patterns of rearing young• Precocial- young can swim, walk,
feed as soon as they hatch (ducks, chickens, etc)
• Atricial- young are born blind, naked, and helpless (hawks, parrots, warblers, etc)
Migration• Migration- seasonal movement
• Ornithologists- study birds
• Earth’s magnetic field changes and gives cues on when to migrate- some monitor position of stars or sun
• Birds eat double before they migrate
REVIEW!!!• In what ways does the gizzard
compensate for the lack of teeth in birds?
• Identify the cues birds use to help them navigate during a migration.