Anatomy of a bird
Form and function
Bird anatomy has unique adaptations helping towards flight.
• A very light skeletal system with powerful musculature
• Circulatory and respiratory systems giving extra lightness, high metabolic rate and oxygen transfer.
• The development of a beak instead of teeth has led to a specialized digestive system.
Skeleton
• Some bones fused into single pieces – so fewer bones than most vertebrates.
• Fused collarbone and keeled sternum (the breastbone) provide attachment for flight muscles.
• Lack a jaw and teeth having evolved a lightweight beak.
Many bones are hollow with cross-struts for strength.
• Some of the hollow bones have air sacs to increase respiratory efficiency and flight.
Muscular System
Birds have about 175 muscles, mainly controlling wings, skin and legs
• PECTORALS control the down stroke of the wings.
• SUPRACORACOIDEUS raise the wing between beats.
Together these muscles make 25 – 35% of the bird’s weight.
• SKIN muscles can adjust and move feathers in flight and at rest.
• Muscles in the PYGOSTYLE [tail bone] control tail movement and spread, vital for changing direction and stopping.
Respiratory System
Birds have a very high OXYGEN DEMAND to sustain flight.
• Birds ventilate their lungs using air sacs acting like bellows forcing air through the lungs.
• Air breathed IN divides, half THROUGH THE LUNGS to anterior (front) air sacs and half goes to posterior (rear) air sacs.
• As air is breathed OUT the posterior air sacs push their air THROUGH THE LUNGS joining the other air being exhaled
So birds receive oxygen breathing in and out.
Circulatory System
Birds have 4-chambered heart as do mammals and crocodiles.
This allows efficient nutrient and oxygen movement throughout the body.
Digestive System
• Most birds have a crop which they fill rapidly with food (owls do not)
• Raptors use powerful beaks to tear flesh into pieces quickly.
• Food stored in the crop is digested later, when the bird is in a safe place.
• Raptors, and many other birds, regurgitate indigestible food parts as a pellet after each meal.
• Most birds, including raptors, drink by scooping water in their beaks and gravity finishes the job.
YOU CAN HELP
None of the above would be possible without the help and support of others. You can make a difference and help us to help them. Whatever you can afford is much appreciated.
We are eternally grateful for those who leave a legacy to the ICBP, as they make a huge difference to our conservation work. For further information please contact us
