2. Class Aves – Birds
Birds (class Aves) are archosaurs but
almost every feature of their reptilian
anatomy has undergone modification in
their adaptation to flight.
3. Class Aves – Birds
Birds are found in most every habitat
from forests to deserts, even in caves.
Some birds dive in the ocean to 45 m to
catch prey.
Birds have visited both the North & South
poles.
The bee hummingbird of Cuba weighs 1.8 g
and is one of the smallest vertebrate
endotherms.
4. Derived Characters of Birds
A bird’s most obvious adaptations for flight are
its wings and feathers.
Feathers are the feature that set birds apart
from other vertebrates.
5. Derived Characters of Birds
Some other theropod dinosaurs had
feathers, but they were not capable of
supporting flight.
Insulation – provides support for the idea
that some dinosaurs were endotherms.
Bright colors may have been used to attract
mates.
6. Characteristics of Birds
All birds also have hind
limbs adapted for walking,
swimming, or perching.
Foot structure in bird feet
shows considerable
variation.
All have keratinized beaks.
All lay shelled amniotic
eggs.
7. The Origin of Birds
Archaeopteryx
The oldest bird known.
Skull similar to modern birds but with thecodont
teeth.
Wings with feathers were present.
8. The Origin of Birds
Much of the skeleton was
that of a theropod
dinosaur.
Long bony tail
Clawed fingers
Abdominal ribs
S-shaped, mobile neck
This fossil demonstrated
the connection between
theropods & birds.
9. Living Birds
The ratites, superorder
Paleognathae, are all
flightless.
Primitive archosaur
palate.
Ostriches, emus, rheas,
kiwis, tinamous.
Flat sternum, poorly
developed pectoral
muscles.
10. Living Birds
All other birds have a flexible
palate.
The demands of flight have
rendered the general body
form of many flying birds
similar to one another.
Flying birds have a keeled
sternum with well developed
pectoral muscles.
11. Living Birds
Flightlessness has
evolved in many groups
of birds.
Penguins (use wings to
swim through water).
Many fossil forms
including flightless owls,
pigeons, parrots,
cranes, ducks, & auks.
Usually occurs on
islands with few
predators.
12. Form & Function – Feathers
Feathers are lightweight,
yet tough, consisting of:
A hollow quill emerges
from the skin.
This becomes the shaft
which bears numerous
barbs that form a flat,
webbed surface, the
vane.
Each barb contains
many barbules.
13. Form & Function – Feathers
Contour feathers are vaned
feathers that cover and
streamline a bird’s body.
Called flight feathers if
they extend beyond the
body.
Down feathers are soft and
have no hooks on barbules.
Filoplume feathers are
hair-like – function unknown.
Powder-down feathers
disintegrate as they grow,
releasing powder that aids in
waterproofing.
14. Form & Function – Feathers
Feathers are homologous to reptiles’
scales.
It develops from an epidermal elevation
overlying a nourishing dermal core.
In reptiles, this elevation flattens into a
scale.
In birds, it rolls into a cylinder and sinks into
the follicle from which it will grow.
15. Form & Function – Feathers
As a feather nears
the end of its growth,
keratin is deposited
to make some of the
structures hard.
The protective
sheath surrounding
the new feather splits
open, and the feather
unfurls.
16. Form & Function – Feathers
When fully grown, feathers are dead –
like mammalian hair.
Birds molt to replace worn out feathers.
Usually feathers are discarded gradually to
avoid bare spots.
Flight feathers & tail feathers are lost in
pairs to maintain balance.
Many water birds lose all their primary
feathers at once and are grounded during
the molt.
17. Form & Function – Feathers
Colors in birds may be pigmentary or
structural.
Red, orange, & yellow are colored by
pigments called lipochromes.
Black, brown, & gray are produced by the
pigment melanin.
Blue is created structurally by the scattering
of shorter wavelengths of light by particles
within the feather.
18. Form & Function – Skeleton
A light, yet still strong skeleton is a
requirement for flight.
Bird bones are laced with air cavities.
20. Form & Function – Skeleton
Birds are archosaurs, and had
ancestors with diapsid skulls.
Bird skulls are highly specialized – mostly
fused into one piece.
Leg bones in birds are heavier – this
helps lower the center of gravity giving
aerodynamic stability.
21. Form & Function – Skeleton
Modern birds are toothless.
Instead they have a keratinized beak.
Most birds have kinetic skulls.
They have a wide gape.
Upper jaw is attached loosely increasing the
gape.
22. Form & Function – Skeleton
All birds that can fly
have a large, thin
keel on their
sternum that
provides area for
the large flight
muscles to attach.
23. Food & Feeding
Early birds were carnivorous, feeding
mostly on insects.
Many birds are still insectivores.
Other foods include nectar, seeds, berries,
worms, crustaceans, molluscs, fish, frogs,
small birds & mammals.
24. Food & Feeding
Some birds are generalists, feeding on
a wide range of food items.
Perhaps more competition for food, but less
danger of something happening to the food
source.
Others are specialists, only feeding on
one type of food.
Less competition, more danger of losing the
food source.
25. Food & Feeding
The beaks of birds are strongly adapted to
specialized food habits.
26. Digestion
At the end of the esophagus of many
birds is the crop.
Used for storage.
27. Digestion
The stomach has two compartments:
The first secretes gastric juices.
The second, the gizzard, is lined with
keratinized plates that serve as millstones
for grinding food.
Birds swallow small stones to help this process.
28. Digestion
Owls can’t digest the bones & fur or
feathers of their prey.
These materials are bundled together and
ejected through the mouth.
Owl pellets can be used to determine what
the owls in a particular area have been
eating.
29. Circulatory System
Birds have a four-chambered heart.
Separate systemic and respiratory
circulations.
Fast heartbeat – faster in smaller birds.
Red blood cells are nucleated and
biconvex.
Mammals are enucleated and biconcave.
30. Respiratory System
The highly adapted respiratory system of
birds is adapted for the high metabolic
demands of flight.
The finest branches of the bronchi are
developed as tubelike parabronchi through
which air can flow continuously – instead of
ending in saclike alveoli as in mammals.
31. Respiratory System
There is an
extensive system
of nine
interconnecting air
sacs that connect
to the lungs.
Air flows to the
posterior air sacs,
to the lung, then
to the anterior air
sacs and out.
32. Respiratory System
The result is that there is an almost
continuous stream of oxygenated air
passing through the highly vascularized
parabronchi.
33. Excretory System
Urine is formed in large, paired
metanephric kidneys.
There is no urinary bladder.
Nitrogenous wastes are secreted as uric
acid rather than urea.
Bird kidneys can only concentrate solutes to
4-8 times that of blood concentration.
34. Excretory System
Some birds,
including marine
birds, have a salt
gland to help rid the
body of excess salts.
Salt solution is
excreted from the
nostrils.
35. Nervous System
Birds have well
developed cerebral
hemispheres,
cerebellum
(important for
coordinating
movement &
balance), and optic
lobes.
36. Senses
Birds usually have poor sense of smell &
taste.
Some, carnivores, waterfowl, flightless birds
have well developed sense of smell & taste.
Birds have the keenest eyesight in the
animal kingdom and also very good
hearing.
A hawk can clearly see a crouching rabbit a
mile away!
37. Flight
To fly, birds must generate lift forces
greater than their own mass and they
must provide propulsion to move
forward.
Bird wings are designed to provide lift.
38. Flight - Wings are Specialized for
Particular Kinds of Flight
Elliptical wings are good for maneuvering in forests.
High speed wings are used by birds that feed during
flight or that make long migrations.
Dynamic soaring wings are used by oceanic birds that
exploit the reliable sea winds.
High lift wings are found in predators that carry heavy
loads. Soaring over land with variable air currents.
39. Migration
Many species of birds
undergo long
migrations using well
established routes.
Some species make
the trip quickly,
others stop along the
way to feed.
Often, they follow
landmarks such as
rivers and coastlines.
40. Migration
The stimulus for
migration has to do
with changing
hormone levels
brought about by a
change in day
length.
41. Migration
Birds navigate using a number of cues:
Visual cues – landmarks.
Accurate sense of time.
Some may use the Earth’s magnetic field.
Celestial cues – sun by day, stars at night.
42. Social Behavior – Mating Systems
Two types of mating
systems found in
birds:
Monogamy where
an individual has
one mate.
Rare in animals,
common in birds.
Seasonal or lifelong
43. Social Behavior – Mating Systems
Birds have a high incidence of
monogamy because both parents are
equally able to perform most aspects of
parental care.
Often success of the hatchlings requires
care from two parents.
44. Social Behavior – Mating Systems
Polygamy where an individual has more
than one mate during a breeding
season.
Polygyny – one male, many females
Polyandry – one female, many males
45. Social Behavior – Mating Systems
The most common
form of polygamy in
birds is polygyny.
In some species, such
as grouse, males
gather in a display
area or lek. Each
male defends part of
the lek and displays
for the females.
Only females care for
young. http://www.youtube.com/watch?v=s2_wdMmEupQ
46. Social Behavior – Mating Systems
An example of polyandry occurs in
spotted sandpipers.
Females defend territories and mate with
several males.
Each male incubates a nest of eggs in the
female’s territory and does most of the
parental care.
This system may have evolved in
response to high predation rates.
47. Nesting
Most birds build nests
in which to lay eggs.
Often great care is
taken to hide the nest,
or make it inaccessible
to predators.
When the young hatch,
they usually must be
fed by one or both
parents.
48. Nesting
Precocial young, such as
ducks, water birds, fowl
and quail are covered
with down when they
hatch and can run or
swim as soon as their
down dries.
Most precocial young
must still be cared for by
the parents for a time.
49. Nesting
Altricial young are naked
and unable to see or walk at
hatching.
They must remain in the nest
for a week or more.
Parents must spend lots of
time & energy bringing food
to hatchlings.
There is a continuum with the
young of many species falling
in between the two extremes.