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While we may never truly understand the reason why the chicken crossed the road, we can tell you more about the body systems that helped them get there. In this section, we will go through the unique features of chicken bones, muscles, and feathers that allow them to navigate their environment.
Birds need to be lightweight so they can fly. Several of their bones including the skull, humerus, clavicle, keel, pelvic girdle and lumbar and sacral vertebrae are pneumatic bones that are air-filled and hooked into the respiratory system. The remaining bones are medullary bones that contain bone marrow and store calcium that laying hens need for making egg shells. The vertebrae in chicken’s necks are freely moveable while the shoulder blades and vertebrae in the spine along their back are fused together into a solid structure to provide better support to the wings. The keel (sternum) is where the muscles from the wings attach so it has a very large surface area.
The breast muscles of chickens are mostly made of white fibres that are able to produce large bursts of speed for very short periods of time while the breast muscles of flying birds are mainly red fibres that allow them to maintain steady movements over longer durations.
Bird feathers are essential for helping them fly. Although chickens are not the most airrworthy birds species, they can reach reasonable heights over short distances.
On the wings, the primaries are the main source of lift that keep birds airborne. Most bird species have 10 primary feathers and will struggle to fly if any of those feathers get damaged. The secondaries also contribute to lift but play a key role in stability and manoeuvrability. The tertiaries are on the rear edge of the wing close to the body of the bird and are not as essential for flight. Coverts help keep the wing in a streamlined shape. The tail feathers also contribute to flight acting like a rudder that allows the bird to twist and turn.