Detection of flow direction in high-flying insect and songbird migrants.
Goal-oriented migrants travelling through the sea or air must cope with the effect of cross-flows during their journeys if they are to reach their destination. In order to counteract flow-induced drift from their preferred course, migrants must detect the mean flow direction, and integrate this information with output from their internal compass, to compensate for the deflection. Animals can potentially sense flow direction by two nonexclusive mechanisms: either indirectly, by visually assessing the effect of the current on their movement direction relative to the ground; or directly, via intrinsic properties of the current. Here, we report the first evidence that nocturnal compass-guided insect migrants use a turbulence-mediated mechanism for directly assessing the wind direction hundreds of metres above the ground. By comparison, we find that nocturnally-migrating songbirds do not use turbulence to detect the flow; instead they rely on visual assessment of wind-induced drift to indirectly infer the flow direction.
Rothamsted Research, Harpenden, Hertfordshire, AL5 2JQ, UK; Environment and Sustainability Institute, University of Exeter, Penryn, Cornwall, TR10 9EZ, UK. Electronic address: jason.chapman@rothamsted.ac.uk.
Jason W
JW
Chapman
Department of Biology, Lund University, SE-223 62 Lund, Sweden.
Cecilia
C
Nilsson
Rothamsted Research, Harpenden, Hertfordshire, AL5 2JQ, UK.
Ka S
KS
Lim
Department of Biology, Lund University, SE-223 62 Lund, Sweden.
Johan
J
Bäckman
Rothamsted Research, Harpenden, Hertfordshire, AL5 2JQ, UK; Natural Resources Institute, University of Greenwich, Chatham, Kent, ME4 4TB, UK.
Don R
DR
Reynolds
Department of Biology, Lund University, SE-223 62 Lund, Sweden.
Thomas
T
Alerstam
Rothamsted Research, Harpenden, Hertfordshire, AL5 2JQ, UK.
Andy M
AM
Reynolds
D025041:Animal Migration; D000818:Animals; D004739:England; D005426:Flight, Animal; D008962:Models, Theoretical; D009036:Moths / Q000502:physiology*; D009949:Orientation; D020308:Songbirds / Q000502:physiology*; D013548:Sweden; D014796:Visual Perception; D014919:Wind