Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Variation of the normalized tail area and flapping angle within one hovering wingbeat cycle. The right side presents schematic of the definition of the flapping angle and varied tail shapes. The error bars indicate s.d. (n = 8). The zone shaded grey corresponds to the period of a downstroke.
