Birds' bones are primarily adapted for flight in several key ways:
-
Hollow Bones: Many bird bones are hollow, which reduces their weight without sacrificing strength. This adaptation helps decrease the overall body weight of the bird, making it easier to achieve and maintain flight.
-
Lightweight Structure: The structure of bird bones includes air spaces and a lightweight composition, which further helps reduce weight. The walls of these bones are reinforced with internal struts to provide strength while keeping the bone light.
-
Strong and Rigid: Although they are hollow, bird bones are still strong and rigid. They are modified to withstand the stresses of flight and landing.
-
Fusion: Some bones in birds are fused together, such as the furcula (the wishbone), which provides additional support and stability during flight.
While cartilage does play a role in the skeletal structure of some birds, the main adaptations for flight involve the hollow and lightweight characteristics of their bones, rather than being primarily made of cartilage or compact bone.
In summary, the correct adaptation related to helping birds fly is that their bones are hollow.