Flap-running in birds is key to flight evolution

BBC : Adult birds will often flap their wings and run up steep inclines rather than fly over them. Brandon Jackson of the University of Montana wanted to know why birds capable of flight use the flap-run motion, writes Victoria Gill for the BBC. To measure birds’ muscle activity, Jackson and his colleagues implanted electrodes into the flight muscles of pigeons. They found that, for birds, running up a ramp with a 65-degree incline requires about 10% as much power from the flight muscles as flying. Flap-running is also a crucial step in learning to fly—young birds that can’t fly yet due to small or weak wings use it to get off the ground and away from predators, transitioning gradually to full flight as they mature. Jackson deduced that dinosaurs with similarly small, weak wings could have also flap-run and transitioned toward flight over evolutionary time.