Birds have a lightweight skeleton made up of bones that are thin and hollow. This helps them fly more easily. While bird bones look different than human bones, they have similar functions and many of the same names.
Skeletal system
Like humans, birds have an internal skeleton made up of bones. There are around 170 different bones in a bird’s body. The skeletal system serves several important functions:
- Supports the body
- Protects internal organs
- Allows movement
- Produces blood cells
- Stores minerals and fat
There are two main parts of a bird’s skeletal system – the axial skeleton and the appendicular skeleton.
Axial skeleton
The axial skeleton forms the central core of the body and includes the skull, backbone (vertebral column), ribs, and breastbone (sternum).
Skull
The skull bones protect the brain and sensory organs like the eyes and ears. Birds have several fused skull bones including the frontal, parietal, nasal, premaxilla, and mandible bones.
Vertebral column
The vertebral column is made up of small interlocking bones called vertebrae. There are three sections:
- Cervical vertebrae – neck bones (14-25)
- Thoracic vertebrae – fused to ribs (6-10)
- Synsacral vertebrae – fused pelvis and spine bones (10-20)
Ribs and sternum
Ribs are thin curved bones attached to the vertebrae. They protect internal organs. The sternum is a flattened bone on the front of the body where the ribs connect.
Appendicular skeleton
The appendicular skeleton includes the bones of the limbs and girdles that connect the limbs to the body.
Pectoral girdle
The pectoral girdle bones include:
- Coracoids – shoulder bones
- Scapula – shoulder blades
- Furcula – wishbone
Pelvic girdle
The pelvic girdle bones include:
- Ilium – hip bones
- Ischium – sit bones
- Pubis – front hip bones
Limbs
Birds have modified forelimbs to form wings. The bones include:
- Humerus – upper arm
- Radius and ulna – lower arm
- Carpometacarpus – wrist/hand
- Digits (fingers) – numbered I, II, III
The hindlimbs consist of:
- Femur – upper leg
- Tibiotarsus – lower leg
- Tarsometatarsus – ankle/foot
- Toes – numbered I, II, III, IV
Special features of bird skeleton
While birds share some bone names with humans, their skeleton has unique adaptations for flight.
Lightweight
Bird bones are hollow inside, which makes them lighter. Air sacs in the bones connect to the lungs and airways. This helps keep the weight down for flying.
Fused bones
Some areas of the bird skeleton have fused bones for added strength to withstand forces from flying. These include:
- Skull bones
- Synsacrum – spine and pelvis
- Pygostyle – fused tail vertebrae
Reduced bones
The clavicles (collar bones) are reduced or missing to allow more flexibility for wing movement.
Breastbone
The breastbone has a large keel that the flight muscles attach to. This provides an anchor for flapping the wings.
Wings
The forelimbs are modified into wings. Important flight feathers attach to the fingers and wrist.
Skeleton of common birds
While all bird skeletons share common features, there are some variations between different groups and species. Here are examples of three common backyard birds:
Cardinal
Cardinals have a lightweight skeleton with a broad sternum to support strong wing muscles for flapping flight. Other features include:
- Long keeled sternum
- Long humerus wing bones
- Reduced clavicles
- Strong leg and toe bones for perching
Sparrow
Sparrows have a compact skeleton well-suited for fluttering flight among trees and shrubs. Features include:
- Small rounded sternum
- Short wingspan
- Long rear toes for gripping
- Short curved beak
Robin
Robins have a versatile skeleton for both open flight and hopping on the ground. Features include:
- Medium keeled sternum
- Partially fused ankle bones
- Straight beak for catching worms
- Long legs for running/walking
Skeleton adaptations
Bird skeletons are precisely adapted for their way of life. Here are some examples:
Bird | Skeletal Adaptations |
---|---|
Eagles | Robust sternum and wings for soaring and lifting prey |
Hummingbirds | Short sternum and wings allow hovering |
Owls | Short tail and flexible neck allow head turning |
Woodpeckers | Short tail braces against tree trunks, sharp beak for chiseling |
Ostriches | Thick strong leg bones support fast running |
Penguins | Short wings for swimming instead of flight, solid bones for diving |
Similarities and differences from human skeleton
When comparing bird and human skeletons, we can see some key similarities and differences:
Similarities
- Basic bone types – both have skulls, spines, ribs, arm and leg bones
- Joints – shoulder, hip, knee, ankle, elbow joints articulate similar to humans
- Skeletal functions – supports structure, allows movement, protects organs
- Some bone names are the same – ex: humerus, ulna, femur, tibia
Differences
- Bird bones are hollow and lightweight
- More fused bones in birds – synsacrum, pygostyle
- Forelimbs modified into wings
- Breastbone with large keel
- No teeth – beaks instead of jaws
- Smaller clavicles
- Shorter tails
- Specialized leg and foot bones
Conclusion
While bird and human skeletons share some similarities, birds have a very specialized skeletal structure to enable flight. Their bones are lightweight and hollow, with fused areas for strength. The sternum, wings, and legs also show specific adaptations for birds’ way of life. So next time you see some bird bones, you’ll know the names for many of them!