User blog comment:Kogath/Monster Hunter XX Discussion/@comment-6050823-20170221060551/@comment-4969421-20170222121548

A flightless bird's airsacs are anatomically and functionally the same as one that flies, because they are part of their respiratory system and although not used for flight, they are still used in actions such as running. However, they tend to have less airsacs to those that fly, for example an ostrich has only 9 airsacs which is the lowest amount a bird can have,and compared to other species' which can have up to 13.