Zoology - BIRDS
THINGS YOU NEED TO KNOW
FROM THIS CHAPTER…
i. How are birds in these
groups different?
ii. What are ratites?
i. I suggest that you make
flashcards. Put the example birds on one
side and the order names on the other.
Then start practicing by flipping through them.
i. Quill
ii. Rachis
iii. Barbs
iv. Vane
v. Barbules
i. Contour
ii. Down
iii. Filoplume
iv. Powder-down
i. How does it usually occur?
ii. Are there any exceptions to
this?
i. As bird weight ______ food
consumption ______.
i. As bird weight ______ heart
rate ______.
CLASSIFICATION OF BIRDS
Phylum Chordata
Class
Aves (**
Only select orders, listed below, need to be memorized.**)
Superorder Paleognathae – Birds with primitive archosaurian
palate. Includes ratites (unkeeled sternum – flightless birds).
Order Struthioniformes
– ostrich of
Order Rheiformes
– rheas of
Order Casuariiformes
– cassowaries & emus of
Order Apterygiformes
– kiwis of
Superorder Neognathae – Birds with flexible
palate
Order Ciconiiformes
– storks, vultures, et al.
Order Anseriformes
– swans, geese, ducks
Order Falconiformes
– eagles, hawks, falcons, condors, &
buzzards
Order Galliformes
– quail, pheasants, turkeys, domestic
fowl, et al.
Order Columbiformes
– pigeons & doves
Order Cuculiformes
– roadrunners et al.
Order Strigiformes
– owls
Order Apodiformes
– swifts & hummingbirds
Order Coraciiformes
– kingfishers et al.
Order Piciformes
– woodpeckers et al.
Order Passeriformes – perching
songbirds
I. Diversity
A. Profile
1. Over ______________
species have been described worldwide.
a. Only __________ have more species among vertebrates.
2. The __________________ is the unique and
essential feature or
hallmark of birds.
3. Uniformity in
Structure
a. Despite 150
million years of evolution, birds are still
readily recognized.
b. Forelimbs are
modified as _______________,
although
not all are capable of flight.
c. Hindlimbs are adapted for walking, swimming or perching.
d. All birds have __________________________________.
e. All birds lay _______________.
f. The driving force
for this uniformity appears to be the
adaptations necessary for ______________________.
1) Wings are present
for support and propulsion.
2) The respiratory
system must meet high oxygen
demands and cool the body.
3) Bones must provide
a light but rigid airframe.
4) Digestion and
circulation must meet the high-
energy demands of flight.
5) And the nervous
system must have superb sensory
systems for high-velocity flight.
II. Origin and Relationships
A. History
1. The discovery of
the fossil of ____________________________
_________________________________ in
linked birds and
____________________________.
a. The skull
resembled modern birds but it had ___________
rather than a beak.
b. The skeleton was
reptilian with clawed fingers, abdominal
ribs and a long bony tail.
c. Feathers were
unmistakably imprinted along the wings.
2. Zoologists had
long recognized that birds and reptiles shared
many similarities.
a. Both have skulls
that abut the first neck vertebra by a
single __________________________________________.
b. Both have a single
middle ear bone, the _____________.
c. The lower jaw in
both is composed of five or six bones; in
mammals there is one mandibular
bone.
d. Both birds and reptiles
excrete nitrogenous wastes as
________________________; mammals excrete urea.
e. Both lay similar yolked eggs; the embryo develops on the
surface by shallow cleavage patterns.
B. Relationships
1. Modern birds
include _________________________________
with a flat sternum and __________________________________
with a keeled sternum.
2. _____________________________
has evolved many times
among many bird groups.
3. Smaller birds can
revert to flightlessness on islands that lack
terrestrial predators.
4. Larger flightless
birds such as the ostrich and emu can outrun
predators.
III. Form and Function
A. Feathers
1. Structure
a. The feather is a
special bird adaptation that contributes to
more power or less weight.
b. The hollow __________________ emerges from the
skin
follicle and continues as a shaft or ____________________.
c. The rachis bears
numerous __________________.
d. Up to several
hundred barbs are arranged to form a flat,
webbed surface, the _____________________.
e. Each barb
resembles a miniature feather; numerous
parallel filaments or ___________________
spread laterally.
f. With up to 600 barbules in each side of a barb, there
may
be over one million in the whole feather.
g. Barbules from two
neighboring barbs overlap; they “zip”
together with tiny hooks.
h. When separated,
they are “zipped” back together by
______________________________.
2. Types of Feathers
a. ________________________ feathers provide the form of
the bird; flight feathers extend off the wing in flight.
b. ___________________ feathers are under
contour
feathers; their barbules lack hooks and they function as
insulation.
c. ________________________ feathers are hairlike,
degenerate feathers with a weak shaft and tuft of short
barbs.
d. ________________________________ feathers on
herons and their relatives disintegrate and release a
talc-like
powder to waterproof feathers.
3. Origin and
Development
a. The bird feather
is homologous to the _______________
_______________.
4. _______________________
– most birds molt once a year,
usually in late summer after the nesting season.
a. The fully-grown
feather is a dead structure; shedding or
molting is an orderly process.
b. Except in
penguins, molting is a gradual process that
avoids leaving bare spots.
c. In many water
birds, primary feathers are molted all at
once and the birds are temporarily grounded, usually
during
nesting.
B. Skeleton
1. Bone Weight
a. Compared with the Archeopteryx, modern birds have light,
delicate bones laced with air cavities.
b. These are termed _________________________ bones;
they are nevertheless strong.
c. The total weight
of a bird’s feathers may outweigh its
skeleton.
2. Bird Skull
a. Bird skulls are so specialized that it is difficult
to see the
diapsid condition.
b. The skull is fused
into one piece; the braincase and orbits
are large to hold a larger brain and eyes.
c. While the skull is
lighter, the legs are heavier than in
mammals; this lowers the _______________________
_____________________.
3. Vertebral Column
and Appendages
a. The bird vertebral
column is very rigid; vertebrae are
fused except for the cervical vertebrae.
b. Except in flightless
birds, the sternum bears a large
_________________ for
anchorage of ________________
________________________.
c. Bones in the
forelimbs are highly modified for flight, with
some bones reduced in number or fused.
C. Muscular System
1. A _________________________ mechanism
prevents a
perching bird from falling off a branch while asleep.
2. As many as 1,000 muscles may control the tail
feathers for
steering in flight.
D. Food, Feeding and
Digestion
1. Insect Eaters (______________________________)
a. In their early
evolution, birds were carnivorous, primarily
feeding on the great variety of insects.
b. Modern birds have
specialized to hunt nearly all types of
insects in most habitats.
2. Other Diets
a. Other animals
joined the diet of birds, including worms,
molluscs, crustaceans, fish, frogs, etc.
b. Nearly one-fifth
of birds feed on ____________________.
c. The beaks of birds
often reveal their food habits and vary
between seed-eaters, insect-eaters, etc.
d. A woodpecker has a
straight, hard, chisel-like beak to
expose insect burrows; its long, flexible, barbed tongue
seeks out the insects in the wood galleries.
3. Food Quantity
a. Contrary to the saying “to eat like a bird” meaning
“to eat
little,” birds are voracious feeders.
b. Birds have a high
metabolic rate and small birds need
even more food per body mass.
c. A hummingbird uses
oxygen _______ times faster than a
pigeon and ________ times that of a chicken.
d. A hummingbird eats
________ of its body weight each
day, a blue tit about ________ and a chicken, _________.
e. Because birds lack
teeth, foods that require grinding are
cut apart in the ______________________.
1)
Birds may also swallow pebbles or grit to assist in
grinding in the gizzard.
f. Many birds have a _______________
that serves to store
food at the lower end of the esophagus.
g. The crop of
pigeons, doves and some parrots, also
produces a lipid- and protein-rich “_____________.”
h. The end of the digestive system is the ______________,
which also receives the products from the genital ducts
and
ureters.
E. Circulatory System
1. The ____________________________ heart is
large, with
strong ventricular walls.
2. Birds share with
mammals a complete separation of respiratory
and systemic circulations.
3. The ____________________________________,
instead of the
left as in mammals, leads to the dorsal aorta.
4. The heartbeat is
relatively fast compared to mammals and is
inversely proportional to size.
a. A turkey heart
beats _______ times per minute.
b. A chicken heart
beats _______ times per minute.
c. A small
black-capped chickadee heart beats ______
times
per minute.
5. Bird red blood
cells (erythrocytes) are nucleated and biconvex.
F. Respiratory System
1. The bird
respiratory system differs radically from the lungs of
both reptiles and mammals.
2. Bird Lungs
a. The finest
branches of the bronchi do not terminate in
alveoli but are tube-like __________________________.
b. _____________________
extend into the thorax,
abdomen, and even the long bones.
c. A large portion of
the air bypasses the lungs and flows
directly to the air sacs on inspiration.
d. On expiration,
this oxygenated air flows through the lungs;
therefore there is continuous air flow.
e. Thus it takes __________ respiratory cycles for a
single
breath of air to pass through the system.
f. This is the most
efficient respiratory system of any
vertebrate.
3. An air sac system
helps cool a bird during vigorous exercise
when up to 27 times more heat is produced.
G. Nervous and Sensory
Systems
1. A bird’s nervous and
sensory system must accommodate the
problems of flight and a visual lifestyle.
2. The bird’s brain
has well-developed cerebral hemispheres,
cerebellum, and midbrain tectum.
3. The cerebral
cortex, a chief coordinating center in mammals, is
thin, unfissured and poorly
developed.
4. Sense of _______________
is poorly developed except in
flightless birds, ducks and vultures.
5. Birds have good
hearing and superb _________________, the
best in the animal kingdom.
6. The bird ear is
similar to the ear of mammals.
a. The external ear
canal leads to an __________________.
b. An inner ear has a short _________________;
it allows
birds to hear about the same range of sound as humans.
c. Bird ears do not
hear as high a frequency as do humans
but surpass us in ability to distinguish differences in
pitch
and intensities.
7. The bird eye is
similar to the mammal eye but it is relatively
larger for a given body size.
a. A bird eye is less
spherical and almost immobile; a bird
turns its head rather than its eyes.
b. Vegetarians must
avoid predators and they have eyes
placed to each side to view all directions.
c. Birds of prey have
eyes directed forward to provide better
depth perception.
d. A hawk has eight
times the visual ________________ of
a human and can see a rabbit over a kilometer away.
e. An owl’s ability
to see in dim light is more than
_________________ that of a human.
f. Many birds can see
partially into the
____________________________ spectrum, seeing flower
nectar guides.
I. Flight
1. History
a. The early airspace
was an unexploited habitat with flying
insects for food.
b. Flight also
provided rapid escape from predators and
ability to travel to better environments.
c. There are two
hypotheses on the evolution of bird flight.
1)
Ground up
2)
Tree down
d. Feathers preceded
flight and arose for thermoregulatory
purposes.
2. Flapping Flight
a. Flapping flight
requires a vertical ___________________
force and a horizontal ________________________ force.
b. Thrust is provided
by ___________________ at the wing
tips and lift is provided by the ___________________.
c. Greatest power is
provided by the
___________________.
d. The _______________________________ is
essential
for hovering and fast, steep takeoffs.
3. Basic Forms of
Bird Wings
a. ___________________ Wings
1) Birds that must
maneuver in
______________________________________
have elliptical wings.
2) Elliptical wings
are slotted between primary
feathers to prevent stalling at low speeds, etc.
3) The small
chickadee can change its course within
0.03 seconds.
b. ___________________ Wings
1) Birds that feed on
the wing or make
______________________________________ have
high-speed wings.
2) These wings sweep
back and taper to a slender tip;
this reduces “tip vortex” turbulence.
3) They are flat in
section and lack wing-tip slotting.
c. ___________________ Wings
1) Albatrosses,
gannets and other oceanic soaring
birds have wings with long, narrow wings.
2) The high-aspect
ratio of long, narrow wings lack
wing slots and allow high speed, high lift and dynamic
soaring.
3) They have the
highest aerodynamic efficiency of
any design, but are less maneuverable.
4) These birds
exploit the highly reliable sea winds,
and air currents of different velocities.
d. ___________________ Wings
1) Vultures, hawks,
eagles, owls and other
______________________________________ that
carry heavy loads have wings with slotting, alulas and
pronounced camber.
2) This produces high
lift at slow speed.
3) Many are land soarers; their broad, slotted wings
allow sensitive response
for static soaring.
IV. Migration and Navigation
A. Migration
1. About ______________
of all bird species migrate.
2. They can move
between southern wintering regions and northern
summer breeding regions.
3. They can exploit
seasonal changes in abundance of insects and
avoid bird predators.
4. Appearing one time
a year prevents buildup of specialized
predators.
B. Stimulus for Migration
1. The long days of
late winter and early spring stimulate
development of gonads and fat.
2. Long day length
stimulates the anterior lobe of the pituitary.
3. Release of
pituitary gonadotropic hormone sets in motion a
complex series of physiological and behavioral changes
resulting in
gonadal growth, fat deposition, migration, courtship, mating
behavior and care of young.
C. Direction Finding in
Migration
1. Experiments
suggest birds navigate chiefly by
___________________.
2. Birds recognize
topographical ___________________
and follow
familiar migratory routes.
3. This pools navigational
resources and also experience of older
birds.
4. Birds also have a
highly accurate innate sense of time and an
innate sense of direction.
5. Research indicates
they can navigate by the
______________________________________; this may be
related to magnetite found in the neck musculature of
pigeons.
6. Sun-azimuth Orientation
a. German
ornithologists used special cages to show birds
navigate by sun at day and stars at night.
b. Planetarium
experiments revealed they use the
___________________ as a compass; an internal clock
tracks position.
c. These experiments
suggest use of the ______________
___________________ as an axis at night.
V. Social Behavior and Reproduction
A. Cooperative Behavior
1. Sea birds often
gather in huge colonies to nest and to rear
young.
2. Birds that isolate
during breeding may congregate for migration
or feeding.
3. There are many
advantages for flocking together:
a. mutual ___________________
from enemies
b. greater ease in finding ___________________
c. less opportunity for an individual ___________________
during migration
d. mass ___________________
for protection against low
night temperatures during migration.
B. Reproductive System
1. Bird testes are
very small until the approach of the breeding
season, when they may enlarge 300 times.
2. Males of most
species lack a penis; mating involves bringing
cloacal surfaces in contact known as _______________________.
3. In
most birds, the ___________________
ovary and oviduct
develop and the right ovary and oviduct degenerate.
4. The expanded end
of the oviduct, the ___________________,
receives the discharged eggs.
5. Special glands add
___________________ or egg white to
the
egg as it passes down the oviduct.
6. Farther down the
oviduct, the shell membrane, shell, and shell
pigments are also secreted.
7. Fertilization must
therefore take place in the upper oviduct before
albumin and shell are added.
8. Sperm remain alive
in the oviduct for many days after a single
mating.
C. Mating Systems
1. Over 90% of bird
species are ________________________;
they only mate with one partner each breeding season.
2. A smaller number are ___________________; individuals mate
with two or more partners each breeding season.
3. The reason birds
have a high monogamy rate, compared to
mammals, is two-fold…
a. Baby birds lack a built-in food supply and require
the parental care from both parents to provision the
young.
b.
1) A male sings often
to announce his presence to
females and drive away males.
2) Females wander
about to select a male that offers
the best chance of reproductive success.
3) Usually a male can
defend an area that provides
just enough resources for one nesting female.
D. Nesting and Care of
Young
1. Nearly all birds
lay eggs that must be incubated by one or both
parents.
2. ___________________ birds are able to
feed and run or swim
as soon as they are hatched.
3. ___________________ birds are naked and
helpless at birth
and must be fed in the nest for a week or more.
4. Nesting success in
altricial birds is very low; sometimes barely
20% of
nests produce young.
5. Causes of nesting
failure include predators, nest parasites and
other factors.
VI. Bird Populations
A. Factors
1. Humans have
introduced birds to new regions; the
___________________ and the ___________________________
are both abundant now in the
2. Since
the dodo went extinct in 1695, more than ______ bird
species have also become extinct due to human influence.
3. Causes of bird
extinction include ________________________
____________________ and ___________________.
4. Modern hunting
interests have helped recover wetlands; no
legally hunted birds are endangered.
5. Recent Decline of
Songbirds
a. Some songbird
species that were abundant 40 years ago
are in decline.
b. ___________________ has utilized
once-fallow fields.
c. ___________________ of forests in the
exposes nests to nest predators.
d. __________________________ are
formidable predators
that kill many songbirds.
e. The loss of
tropical forests also deprives about 250
migratory songbirds of their wintering homes.