White-fronted goose migrating in a formation flight riding on a fair wind

　The goose is a bird with long arm and split wing, similar to a great egret, and it makes the beating of two hinges. In the flapping up run, the secondaries are flapped up first, and then the primaries are shifted in parallel with the tip velocity of the secondaries. Then the goose makes stop the secondaries and flap up the primaries. By such a flapping up, the negative thrust should be suppressed in minimum. The following birds in a formation flight would omit the later half in the flapping up run, because of the reduction in the induce drag. 　The geese migrating in a formation flight to the direction of the streaming cloud is the famous natural features of the season. 　(Prod. Jun. 2007, scale 1/2, No.1)