MAINE SUNDAY TELEGRAM • July 23, 2023
Humans (mammals) have a bidirectional airflow: we inhale oxygen into our lungs, where in smaller air sacs the gas exchange of oxygen and carbon dioxide occurs. It takes our exhale to release that carbon dioxide, making it a moment when we are deprived of oxygen. Birds, on the other hand, need to be more efficient, especially when doing things like flying, and so have evolved non-inflatable lungs with nine air sacs that allow for unidirectional airflow. It requires birds to take two breaths to have a complete respiration cycle, but thanks to this unidirectional flow, birds basically never need to “catch their breath.” ~ Maine Audubon Staff Naturalist Doug Hitchcox