Transcript The Bird Body

The Bird Body
Characteristics of Birds
• All birds are members of the class Aves
• Birds have retained some reptilian
characteristics
– Amniotic eggs
– Feet and legs of birds are covered in scales
Characteristics of Birds
• All birds share similar characteristics:
– Feathers that cover the body
– Wings
– Lightweight skeleton
– Endothermic metabolism (warm-blooded)
– Lungs with air sacs
– A Beak
Body Temperature and Control
• Birds are endothermic
– They generate enough heat through metabolism to
maintain a high body temperature
– Their environment does not determine body temp.
• Normal body temp. is 40-44 degrees Celsius
– Body temp is significantly higher than mammals body
temp (37 degrees Celsius)
• Birds have high body temp. due to a fast
metabolism
Energy to Fly
• A quick and efficient digestive system allows
birds to obtain enough energy to fly and
maintain their body heat
– Some eat up to ½ their body weight in a day
• Food passes quickly through the digestive
system
– Ex. A Thrush can eat blackberries, digest the, and
excrete the seed 45 minutes later
• It would take humans 12 hours
Adaptations for Birds
• Flight requires a number of special
adaptations
– Feathers
– A strong, lightweight skeleton
• Other adaptations include:
– A bird’s beak and feet
– Both are adapted to the food the bird eats and the
environment they live in
Feathers
• Birds have two main types of feathers
1. Contour Feathers
2. Down Feathers
Contour Feathers
• Contour Feathers cover an adult bird’s body
– Contour feathers on the tails and wings are called
flight feathers, and provide lift for flight
– Contour feathers have many branches called
barbs
– Barbs are linked together giving the feather a:
• smooth surface
• sturdy flexible shape
Contour Feathers
Down Feathers
• Down Feathers cover the body of young birds
and are found beneath adult bird’s contour
feathers
• Down Feathers trap warm air and conserve
body heat
Lightweight Skeleton
• Bones of birds are thin and hallow
• Many of the bones are fused
– More rigid skeleton than reptiles
– Creates a sturdy frame that anchors muscles
during flight
Breastbone and Muscles
• Power of flight comes from the large breast
muscle
– Makes up 30% of a bird’s weight
– Muscles stretch from the wing to the breastbone
• The breastbone is very large and bears a
prominent keel
– Keel resembles the v-shape bottom of a boat
• Muscles are attached to the keel and to the fused
collarbones
– **NO other vertebrates have fused collarbones or a
keeled breastbone**
Keel Shaped
Breastbone
Beaks and Feet
• Birds are adapted for different ways of life
• You can learn a great deal about a bird’s diet
and habits by examining the bird’s beak, feet,
and legs
Perching and Flightless Birds
• Feet:
– Perching birds:
• Have curved toes for holding onto branches
– Flightless birds:
• Have strong legs and feet with thick toes that are
modified for running
Perching and Flightless Birds
• Beaks:
– Perching Birds:
• May be short and thick, which allows crushing of
seeds
Ex. Canary
• Long, thin, beaks for drinking nectar
Ex. Humming birds
• Long, strong beaks for snatching insects out of the
air
Ex. Woodpeckers
Marsh Birds and Water Birds
• Feet:
– Marsh Birds:
• Have long toes that keep them from sinking into the
mud
• Have long legs to keep the bird’s body above water
• Very clumsy when they try to land in trees
– Water Birds:
• Webbed feet – used for paddling
• Have trouble perching in trees
Marsh Birds and Water Birds
• Beaks:
– Marsh Birds:
• long beaks for catching fish or digging in mud for
worms
– Water Birds:
•
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Rounded beaks for eating plants
Long beaks for eating fish
Hooked beaks to grip slippery prey
Sharp beaks used to spear fish
Review Questions
• 1. Summarize how birds obtain the energy
necessary for flight
• 2. Identify a bird’s adaptations for flight
• 3. Write a paragraph (3/4 of a page long)
about the following
– Some biologists have proposed that birds and
reptiles should be grouped in the same class of
vertebrates. Do you Agree? Support your answer
with at least 5 reasons.
Respiration and Circulation
• The following respiratory and circulatory
structures help all birds obtain the energy
they need
– Air sacs
– Four chambered heart
• They also improve oxygen intake and delivery
Air Sacs
• Birds have air pass over the lung surface’s in
one direction
– Air sacs allow one-way air flow
– Air sacs act as holding tanks for air
• Advantages to one-way air flow
1. Lungs only exposed to fresh air, increasing
the amount of oxygen that can be absorbed
2. Blood and air can flow in different directions,
allows increase in oxygen absorption
Four- Chambered Heart
• Blood enters the right atrium
• Specialized tissue lies in the muscular wall of
the right atrium
– Heartbeat originates in this tissue
– Tissue known as the pacemaker
• A bird’s heart rate can be extremely high in
order to pump large amounts of oxygen to the
bird’s body
Four- Chambered Heart Structure
• Ventricle is divided into a right and left by the
septum
• Allows oxygen rich and oxygen poor blood to
remain separate
– Allows oxygen to be delivered to the body cells
more efficiently
Reproduction
• Reproduce through internal fertilization
• During mating male birds press their cloaca to
the female’s cloaca and releases sperm
• Produces amniotic eggs
– May lay one egg or a clutch of several eggs
Parental Care
• Most birds care for their eggs and their young
• Birds usually lay their eggs in nests
– Hold eggs and conceal them from predators and
other elements
– Nests are built from available materials
• Twigs, barks, grasses, feathers…etc.
• One or both of the parents warm, or incubate,
the egg by sitting on them
Bird Mating
• Most species of birds form pairs that are made
up of male and female
– May spend their entire lives together and defend
a single territory
• However, eggs may be fertilized by several
different fathers
– Usually leads to extensive parental care
Parental Care
• Three options for parental care
1. Only one parent takes care of the egg
Ex. African Jacana
2. Caring for hatchling is an affair for the entire family
(parents, siblings, …etc).
3. No care for the young
Ex. Brown-headed Cowbirds will lay their eggs in other bird’s
nests and let other birds raise their young
Review Questions
• 1. Explain the functions of the anterior and
poster air sacs
• 2. In paragraph form Describe reproduction
and parental care in birds
• 3. Why is it advantageous for birds to be
oviparous rather than ovoviviparous? What’s
the difference between oviparous and
ovoviviparous?