Flight Orientation Behaviors Promote Optimal Migration Trajectories in High-Flying Insects

Not at the Mercy of the Wind How can insects that migrate at high altitudes on fast-moving winds influence their direction of migration, when wind speeds typically exceed their self-propelled air speeds by a factor of three or four? Using automated vertical-looking entomological radar systems, Chapman et al. (p. 682) show that compass-mediated selection of favorable tailwinds, and partial correction for crosswind drift, are widespread phenomena in migrant insect species. Specialized flight behaviors have decisive influence on the migration pathways achieved by insects. Thus, contrary to popular belief, migrant insects are not at the mercy of the wind. Radar reveals that insects use high-altitude winds and correct for crosswind drift during long-range migrations. Many insects undertake long-range seasonal migrations to exploit temporary breeding sites hundreds or thousands of kilometers apart, but the behavioral adaptations that facilitate these movements remain largely unknown. Using entomological radar, we showed that the ability to select seasonally favorable, high-altitude winds is widespread in large day- and night-flying migrants and that insects adopt optimal flight headings that partially correct for crosswind drift, thus maximizing distances traveled. Trajectory analyses show that these behaviors increase migration distances by 40% and decrease the degree of drift from seasonally optimal directions. These flight behaviors match the sophistication of those seen in migrant birds and help explain how high-flying insects migrate successfully between seasonal habitats.