1. Adaptations for flight
Skeleton strengthened
ribs have rear-facing uncinate processes that overlap and strengthen walls of thorax
bones of wrist, pelvis fused
Sternum or breastbone enlarged with a large keel (carina) for attachment of massive flight muscles -- pectoralis and supracoracoideus.
Fused hand bones support and maneuver primary flight feathers.
Efficient lungs and powerful four-chambered heart power flight.

2. Skeleton Strong yet light bones Pneumatized space with cross struts
Spaces extend to air sacs of respiratory system
Birds not any lighter than other mammals of same size
Distribution of weight over legs provide lower center of gravity
Aerodynamic stability

4. FUSED BONES = Sturdy FURCULA PYGOSTYLE STERNUM
Image modified from:

5. Muscles Pectoralis major
Downward beat of flight
Connects humerus with keeled sternum.
Surpacoracoideus(Pectoralis minor) raises wings
-Pectoralis minor connect coracoid bone with keeled sternum

6. Further skeletal modifications for flight: Triosseal canal
Trisosseal canal. The triosseal canal is formed by the junction of the coracoid, scapula and furcula. The supracoracoideus tendon passes through this canal up from the supracoracoideus and inserts on the dorsal face of the humerus.
Dorsal insertion allows triosseal canal to act as a pulley and the supracoracoideus can lift the wing during the recovery stroke.

7. Triosseal Canal. http://www. palaeos

8. Feet Mostly bone, scales and skin
Keeps bird from feeling cold and heat at foot
Perching due to special tendons

9. Feeding & Digestion Large appetites due to high metabolic requirements
No teeth
Gizzard for grinding (keratinized plates)
Proventriculus adds gastric juices
Crop stores food
Caeca – where small intestine joins cloaca
Hold bacteria in herbivorous birds
Young birds have bursa of Fabricius
Process B cells of immune system

11. GIZZARD
Muscular
Contains gravel/rocks
to grind food

12. Circulatory System 4 chambered heart Closed system
Separation of respiratory and systemic circulations
Right aortic arch leads to dorsal aorta (left in humans)
Larger the bird, slower the heartbeat
Nucleated erythrocytes

14. Respiratory System Nine air sacs Fresh air always moving
Connect to lungs and centers of bones
Cools the bird
Fresh air always moving
No dead ends as in mammals
Each wing beat moves air
Never run out of air

17. Excretory System Paired metanephric kidneys
Selective re-adsorption of solutes
Urine formed and passed via ureters to cloaca
No urinary bladder
Water removed in cloaca and forms uric acid
Salt glands, particularly in sea birds

18. Nervous and Sensory System
Need well developed brain
Cerebral hemispheres, cerebellum and optic lobes
Cerebral cortex less developed
Cerebellum coordinates
Muscle position
Equilibrium
Visual clues
All necessary for movement and balance
Poor sense of smell and taste (carnivorous, flightless, oceanic and waterfowl have good tasting ability
Hearing good

19. Vision Similar to humans Rods & cones
Highly vascularized area near optic nerve called pecten (adds additional nutrients to eye)
Fovea may be found in pits on retina
Some birds have two fovea
Binocular vision birds
Central fovea for sharp monocular images
Posterior fovea for sharp binocular vision

20. Reproduction Males with paired testes
Females often have only left ovary and oviduct
Egg captured by oviduct (infundibulum)

21. Flight
Bernoulli Effect

22. 19.13

24. Migration
Travel to warmer climates when food supply dwindles & temperature drops
Rely on fat reserves to make the trip
How do birds navigate the long trips?
Monitor position using sun/stars
Topographical landmarks (mountains)
Earth’s magnetic field
Low frequency sounds
Changes in air pressure with altitude

25. Migration & Navigation
Most have established routes
½ of all species migrate
Most from north to south in fall and south to north in spring
Parameters of migration
Use of different routes in fall and spring
Time to complete route
Night vs day migration (or both)
Distance of migration
Use of landmarks

26. 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.

27. Migration
The stimulus for migration has to do with changing hormone levels brought about by a change in day length.

28. Direction Finding Factors Use of topographical landmarks
Flock behavior by following experienced birds
Innate sense of time
Use of earth’s magnetic field
Celestial clues (both stars and sun)
Sun-azimuth orientation (use of sun and innate sense of time)