2. Birds
Arguably the most noticeable and
melodious of vertebrates
- 10,500 species
- Worldwide in distribution
3. Birds
Feathers are the primary distinguishing
feature
- If have feathers = bird
- If lack feathers ≠ bird
- True today, but not in the past
- Increasing evidence that many
dinosaurs were feathered
4. Birds
Feathers are the primary distinguishing
feature
- If have feathers = bird
- If lack feathers ≠ bird
- True today, but not in the past
- Increasing evidence that many
dinosaurs were feathered
5. Birds
General characteristics
- Great uniformity of structure
- Easy to recognize “a bird”
- Forelimbs modified into wings
- Though flying ability might have been lost
- Hindlimbs adapted for walking,
swimming, or perching
- Keratinized beak lacking teeth
- Egg laying
Uniformity a result of constraints of flight
6. Birds
Flight has shaped avian anatomy
- Wings for lift, propulsion, and steering
- Light yet rigid airframe
- Highly efficient respiratory system
- Rapid and efficient digestive system
- High pressure circulatory system
7. Origin and relationships
Archaeopteryx lithographica
- Fossil showing transition between dinosaurs and birds
- Reptilian features
- Teeth
- Long bony tail
- Abdominal ribs
- Clawed fingers
- Avian features
- Feathers
8. Origin and relationships
Similarity of birds and nonavian reptiles long noted
- Single occipital condyle
- Single middle ear bone
- Lower jaw of several bones
- Uric acid
- Large, yolked eggs
9. Origin and relationships
Feathers came long before flight
Dromaeosaurs (includes Velociraptor)
- Furcula
- Lunate wrist bones
- Feathers on Sinosauropteryx, Protarchaeopteryx,
and Caudipteryx
10. Origin and relationships
Living birds separated into two groups
- Palaeognathae - large, flightless birds
- Flat sternum and poorly developed pectoral muscles
- Neognathae - all other birds
- Keeled sternum and well developed pectoral muscles
11. Structural and functional adaptations for flight
Feathers
- Calamus
- Rachis
- Barb
- Barbule
- Vane
12. Structural and functional adaptations for flight
Feathers
- Types of feathers
- Contour
- Flight feathers
- Primaries
- Secondaries
- Tail
- Down feathers
13. Structural and functional adaptations for flight
Skeleton
- Pneumatized bones
- Light but strong
- Skeleton no lighter than mammal’s, but weight
concentrated under center of gravity
- Vertebral column is fused and rigid
- Cervical vertebrae have high mobility
- Caudal vertebrae fused into pygostyle
- Synsacrum represents the vertebrae of the trunk
14. Structural and functional adaptations for flight
Skeleton
- Uncinate processes link ribs together
- Sternum has large keel (carina)
- Attachment for pectoral muscles
- Elastic furcula
- Helps to lift wings
- Fusion and reduction in number of hand bones
- Carpometacarpus
15. Structural and functional adaptations for flight
Muscular system
- Pectoralis major
- Downstroke
- Supracoracoideus
- Upstroke
- Leg muscles are concentrated near the top
- Foot almost devoid of muscles
16. Structural and functional adaptations for flight
Food, Feeding, and Digestion
- Early birds were carnivorous
- Today, eat almost all types of plant and animal
matter
- Beaks (bills) of birds strongly adapted to food
habits
17. Structural and functional adaptations for flight
Food, Feeding, and Digestion
- Digestion is fast
- Crop as storage organ
- Stomach separated into proventriculus
and ventriculus
18. Structural and functional adaptations for flight
Circulatory system
- Similar to that of mammals
- Yet independently derived
- Four-chambered heart
- Complete separation of oxygenated and deoxygenated blood
- Pulmonary and systemic circuits
- High blood pressure
- Rapid heartbeat
- Chicken : 250 bpm rhr
- Songbird: 500 bpm rhr
20. Structural and functional adaptations for flight
Respiratory system
- Differs greatly from other lung breathers
- Unidirectional flow
- Mammals have bidirectional flow
- Use of air sacs (n = 9)
- Two cycles for a single breath to pass through
21. Flight
Two competing hypotheses for origin of
flight
- Tree down
- Bird flight evolved from gliding
- Ground up
- Bird flight evolved from running and
jumping
Both hypotheses attempt to explain the
utility of half a wing
- WAIR
- Use of protowings to to scale inclines
22. Migration
Not unique to birds
- Birds use numerous compasses
- Solar
- Stellar
- Magnetism
- Visual landmarks
23. Reproduction
Male
- Testes not maintained throughout the year
- May swell 300 times during breeding season
Female
- Generally only 1 ovary (left side)
- Eggs endowed with yolk, albumen, shell membranes, and shell
24. Reproduction
Mating systems
- Birds exhibit a wide variety of mating systems
- Monogamy
- May be social or genetic
- Promiscuity
- Typified by lek mating birds
- Polyandry
- 1 female, multiple males
- Polygyny
- 1 male, multiple females
25. Reproduction
Eggs laid into clutches (the collection of
eggs)
- Incubation required for development
- Exceptions are megapods who use rotting
vegetation to incubate
- Incubation length varies among life
history strategies
26. Reproduction
Young birds
- Precocial: long incubation period, short nest period for young, well developed
at hatching
- Altricial: short incubation period, long nest period for young, poorly developed
at hatching
