1. The Bird Body

2. 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

3. 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

4. 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 degrees Celsius
Body temp is significantly higher than mammals body temp (37 degrees Celsius)
Birds have high body temp. due to a fast metabolism

5. 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

6. 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

7. Feathers Birds have two main types of feathers 1. Contour Feathers
2. Down Feathers

8. 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

9. Contour Feathers

10. 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

11. 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

12. 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**

13. Keel Shaped Breastbone

14. 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

15. 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

16. 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

17. 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

18. Marsh Birds and Water Birds
Beaks:
Marsh Birds:
long beaks for catching fish or digging in mud for worms
Water Birds:
Rounded beaks for eating plants
Long beaks for eating fish
Hooked beaks to grip slippery prey
Sharp beaks used to spear fish

19. 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.

20. 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

21. 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

23. 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

24. 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

26. 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

27. 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

28. 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

29. Parental Care Three options for parental care
Only one parent takes care of the egg
Ex. African Jacana
Caring for hatchling is an affair for the entire family (parents, siblings, …etc).
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

30. 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?