edge-of-existence-edge:The northern brown kiwi is a flightless bird. It has no keelbone to anc
edge-of-existence-edge:The northern brown kiwi is a flightless bird. It has no keelbone to anchor its wing muscles, and its wings have become so reduced that they are almost invisible under their hair-like feathers. Unlike most birds, which have hollow bones, kiwis actually have bone marrow, just as mammals do. -- source link