Ancient murrelet in beating flight at sea

　In air of lower density compared with sea water, the fully opened primaries and secondaries produce the lift and the thrust. The deficiency of the lift and the thrust must be made up by enhancing the amplitude and frequency of the flapping, and also the surface effect must be used by skimming flight over sea. Because it is impossible to incline the wing under the surface effect, the steerage must be attained only by the feet. A sharp steerage might be possible, if made use of a touch with sea. (Prod. Oct. 2005, full‐scale, No.1)