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Frigatebirds follow Lagrangian Coherent Structures (alternative title: Flying on top of ocean highways)

By E. Hernandez-Garcia, C. Lopez, E. Tew Kai, F. Marsac , V. Rossi, V. Garçon, J. Sudre, H. Weimerskirch
Talk presented at LAPCOD2009 2009

We have analyzed meso- and submesoscale Lagrangian structures in the surface of the Mozambique Channel, as revealed by Finite-Size Lyapunov exponents (FSLEs), over a 2-month observation period, and compared them with ARGOS-tracked flying trajectories of a marine predator, the Great Frigatebird. We find that frigatebirds track precisely FSLE ridges, which reveal Lagrangian Coherent Structures. They do so while  foraging, but also while performing long displacements between foraging and nest sites. The birds might use visual and/or olfactory cues and/or atmospheric current changes over the structures to move along these biological corridors. Comprehension of this behaviour would be important not only to seabirds´ ecology but for the understanding of the full Channel ecosystem.

Tew Kai at al., PNAS 106, 8245-8250 (2009)