Cranes soar on thermal updrafts behind cold fronts as they migrate across the sea

Sasha Pekarsky*, David Shohami, Nir Horvitz, Rauri C.K. Bowie, Pauline L. Kamath, Yuri Markin, Wayne M. Getz, Ran Nathan*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Thermal soaring conditions above the sea have long been assumed absent or too weak for terrestrial migrating birds, forcing obligate soarers to take long detours and avoid sea-crossing, and facultative soarers to cross exclusively by costly flapping flight. Thus, while atmospheric convection does develop at sea and is used by some seabirds, it has been largely ignored in avian migration research. Here, we provide direct evidence for routine thermal soaring over open sea in the common crane, the heaviest facultative soarer known among terrestrial migrating birds. Using high-resolution biologging from 44 cranes tracked across their transcontinental migration over 4 years, we show that soaring performance was no different over sea than over land in mid-latitudes. Sea-soaring occurred predominantly in autumn when large water-air temperature difference followed mid-latitude cyclones. Our findings challenge a fundamental migration research paradigm and suggest that obligate soarers avoid sea-crossing not due to the absence or weakness of thermals but due to their low frequency, for which they cannot compensate with prolonged flapping. Conversely, facultative soarers other than cranes should also be able to use thermals over the sea. Marine cold air outbreaks, imperative to global energy budget and climate, may also be important for bird migration.

Original languageAmerican English
Article number20231243
JournalProceedings of the Royal Society B: Biological Sciences
Volume291
Issue number2015
DOIs
StatePublished - 17 Jan 2024

Bibliographical note

Publisher Copyright:
© 2024 The Author(s) Published by the Royal Society. All rights reserved.

Keywords

  • Grus grus
  • ecological barrier
  • mid-latitude cyclones
  • movement ecology
  • sea-crossing
  • soaring-gliding

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