Figure 2.

Some orientation responses to wind flow in high-flying migrant insects. Each diagram shows the wind-flow vector (solid black line), the heading vector (solid coloured line, not present in strategy 1 ‘passive downstream movement’) and the resultant track (= displacement) vector (dashed coloured line). The dotted grey line shows the preferred direction of movement (PDM) for those strategies which imply that the insect has one (strategies 3–5 only). Strategy 5 is a variant of ‘full drift’ in which orientation in a seasonally preferred direction has a significant upwind component (in light winds from various directions). Modified from Chapman et al. [35].