Directional bias as a component of social behaviour with special reference to the Mallard, Anas platyrhynchos



Three types of “shake”, given by male Mallards, Anas platyrhynchos, during Social Display, exhibit a crious “directional bias” in that the first sideways turn of the head tends to be made towards one of the females present. An investigation of the phenomenon by means of film suggests that directional bias reliably reflects a male's “interest” in a particular female. Evolutionary implications and the possible role of directional bias in social communication are briefly discussed.