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.