Flightlessness in birds is known to be related to changes in the pectoral girdle, flight feathers and body size, and was once speculated to also be related to brain size in birds.
Flightlessness in birds is known to be related to changes in the pectoral girdle. Flightlessness in birds is known to be related to changes in flight feathers. Flightlessness in birds is known to be related to changes in body size. Flightlessness in birds was once speculated to also be related to brain size in birds.