Lesson 23 Outline list Lesson 25
Fundamentals of Biology
Lesson 24
Birds
I. General Characteristics.
A. 2 wings and 2 legs.
B. Covered with feathers (the only animals with feathers).
C. Strong, light-weight skeleton.
D. Rapid, efficient digestion.
E. High metabolism.
F. Endothermic.
G. Air sacs.
H. 4-chambered heart.
I. Oviparous.
J. Internal Fertilization.
II. Feathers.
A. General Characteristics.
1. Grow from the papilla in the skin.
2. A large bird may have up to
25,000.
B. Parts.
1. Shaft.
a. Quill.
b. Rachis.
2. Vane.
a. Parallel
rows of barbs perpendicular to the shaft.
b. Parallel
rows of barbules perpendicular to each barb.
C. Care.
1. Stroking reattaches the barbules.
2. Preening is the application of
oil.
a. Prevents
the feather from becoming brittle.
b.
Waterproofs the feather.
c. Gland at
the base of the tail produces oil.
D. Types.
1. Down.
a. Barbules
do not interlock.
b. This makes
them fluffy instead of smooth.
c. Provide
insulation.
2. Contour.
E. Molting.
1. Often occurs in late summer before
migration.
2. Flight feathers molt 2 at a time,
one on each side, to maintain balance.
III. Wings.
A. Elliptical.
1. Short and wide.
2. Quick take-off and landing,
low-speed flight, great maneuverability.
3. Sparrow, woodpecker.
B. High-speed.
1. Thin, long, tapered.
2. Minimum drag.
3. Tern, swift.
C. Soaring.
1. Long, thin, like a glider.
2. Stay aloft with minimum energy.
3. Gull.
D. High-lift.
1. Large, convex, great lift.
2. Enable to carry large prey.
3. Hawk, owl, eagle.
IV. Feet.
A. Wading.
1. Long, thin, widely spaced toes;
thin legs.
2. Distribute weight to prevent
sinking in the mud.
3. Move through water without
creating turbulence.
4. Stork, crane, flamingo.
B. Swimming.
1. Webbed feet.
2. Paddle in water.
3. Duck, goose.
C. Climbing.
1. 2 front toes, 2 rear toes; short
and sharp.
2. Grip vertical surfaces.
3. Woodpecker.
D. Running.
1. Long, thick, muscular.
2. Ostrich.
E. Grasping.
1. Talon-tipped.
2. Clamp onto and pierce prey.
3. Falcon, eagle.
F. Perching.
1. 3 front toes, 1 rear toe, with a
“locking device.”
2. Keeps bird on its perch, even
while sleeping.
3. Robin, wren.
V. Beaks.
A. Spearing.
1. Long, slender.
2. Spear fish in the water or pluck
insects from tree bark.
3. Stilt.
B. Cracking.
1. Short, thick.
2. Cracking and crushing seeds.
3. Cardinal, bunting.
C. Predatory.
1. Hooked, pointed.
2. Tearing prey apart.
3. Hawk, eagle.
D. Filtering.
1. Large, with a built-in sieve.
2. Separate tiny plants and animals
from water.
3. Flamingo.
VI. Skeleton.
A. Jaws are elongated to form the bill.
B. Many neck vertebrae.
1. Very flexible neck.
2. Useful in manipulating objects
with the head.
3. Compensates for immovable eyes.
C. Trunk vertebrae, ribs, and sternum (breast bone) are fused to make a rigid “cage.”
D. Large sternum has a ridge (keel) where flight muscles are attached.
VII. Digestion.
A. High metabolism required by high body temperature and
high energy demands of flight.
1. Young birds may eat more than
their own weight in a day.
2. Rapid digestion.
a. Thrush
digests berries in 30 minutes.
b. Shrike
digests a mouse in 3 hours.
B. Digestive tract.
1. Esophagus.
2. Crop: storage.
3. Stomach: secretes digestive
juices.
4. Gizzard: grinds food.
5. Intestine: absorbs nutrients.
6. Rectum.
7. Cloaca.
VIII. Respiration.
A. Air sacs attached to lung.
1. 25% of incoming air goes to the
lung, 75% goes to the air sacs.
2. Air sacs empty air into the lungs
during exhalation.
3. Thus O2 is absorbed during both
inhalation and exhalation.
4. Air sacs also lighten the weight
of the bird.
B. Respiration is bird’s primary means of cooling the body.
C. Songs are produced by the syrinx, an enlargement of the trachea.
IX. Circulation.
A. 4-chambered heart keeps oxygenated blood separated from
deoxygenated blood.
B. High metabolism requires rapid circulation: 135 to 1,000
beats per minute.
X. Senses.
A. Good hearing.
B. Best eyes in the Animal Kingdom.
1. Usually immovable.
2. Usually set on either side of the
head.
a. Wide field
of vision.
b. Poor
perspective.
c. Some, like
the owl, have eyes in the front of the head and do have perspective vision.
XI. Reproduction.
A. Courtship.
1. Dazzling appearance.
2. Song.
B. Internal fertilization of amniotic eggs.
C. Care of the young.
1. Most eggs require incubation,
usually by parent(s) sitting on them.
2. Altricial chicks.
a. Less than
2 weeks incubation.
b. Hatch
naked, blind, helpless.
c. Parents
feed until they are feathered and able to fly.
d. Less than
6 eggs per year.
e. Robin,
thrush, sparrow.
3. Precocial.
a. Longer
incubation.
b. Hatch able
to move and feed themselves.
c. Stay close
to parents for protection.
D. Reproductive Cycle.
1. Usually 1 year.
2. Most birds choose a different mate
each year.
3. Some, like eagle, mate for life.
XII. Migration.
A. Enables birds to live in a warm climate all year.
B. Enables them to nest in the north where days are long and
predators are few.
C. Prompted by length of days.