title: The role of the US Great Plains low-level jet in nocturnal migrant behavior.
abstract: The movements of aerial animals are under the constant influence of atmospheric flows spanning a range of spatiotemporal scales. The Great Plains nocturnal low-level jet is a large-scale atmospheric phenomenon that provides frequent strong southerly winds through a shallow layer of the airspace. The jet can provide substantial tailwind assistance to spring migrants moving northward, while hindering southward migration during autumn. This atmospheric feature has been suspected to play a prominent role in defining migratory routes, but the flight strategies used with respect to these winds are yet to be examined. Using collocated vertically pointing radar and lidar, we investigate the altitudinal selection behavior of migrants over Oklahoma during two spring and two autumn migration seasons. In general, migrants choose to fly within the jet in spring, often concentrating in the favorable wind speed maximum. Autumn migrants typically fly below the jet, although some will rapidly climb to reach altitudes above the inhibiting winds. The intensity of migration was relatively constant throughout the spring due to the predominantly favorable southerly jet winds. Conversely, autumn migrants were more apt to delay departure to wait for the relatively infrequent northerly winds.
authors.affiliation: School of Meteorology, University of Oklahoma, Norman, OK, USA. charlotte.wainwright@ou.edu.|Rothamsted Research, Harpenden, AL5 2JQ, UK. charlotte.wainwright@ou.edu.
authors.forename: Charlotte E
authors.initials: CE
authors.lastname: Wainwright
authors.affiliation: School of Meteorology, University of Oklahoma, Norman, OK, USA.|Advanced Radar Research Center, University of Oklahoma, Norman, OK, USA.|Rothamsted Research, Harpenden, AL5 2JQ, UK.
authors.forename: Phillip M
authors.initials: PM
authors.lastname: Stepanian
authors.affiliation: Advanced Radar Research Center, University of Oklahoma, Norman, OK, USA.|Oklahoma Biological Survey, Norman, OK, USA.|Department of Biology, University of Oklahoma, Norman, OK, USA.
authors.forename: Kyle G
authors.initials: KG
authors.lastname: Horton
mesh_terms: D000531:Altitude; D025041:Animal Migration; D000818:Animals; D001717:Birds; D005426:Flight, Animal; D007313:Insecta; D009825:Oklahoma; D012621:Seasons; D014919:Wind
keywords: Aeroecology; Lidar; Low-level jet; Migration; Radar; Wind assistance