[Tweeters] Shearwater Dynamic Soaring

[Denis DeSilvis]

Tweeters,
For those of you interested in pelagic birding, you might find the full article (link at bottom) interesting. You can glean some interesting facts going through the paper, if you parse past the math. Hey, some of you might like the math! (I found the item that "specializations of the visual field in Procellariiformes, which have a horizontal streak where the retinal ganglion density is higher, thereby improv[es] resolving power around the horizon." Wow!)

There is a secret source of energy above the sea's surface called the shear gradient. This is where the wind speed is slow just above the surface and becomes progressively faster with height. In 1883, the physicist Lord Rayleigh devised the theory of dynamic soaring which says that a bird ascending into - and descending with - the shear gradient, can harvest such an energy source. This is what albatrosses do, and that leads to the corkscrewing trajectories that albatrosses fly over the ocean surface. Manx Shearwater fly similar trajectories, but also flap, and researchers have now shown that this is the same dynamic soaring flight as the albatross, albeit combined with flapping. What's more, harvesting energy in this way appears to influence the directions that Manx Shearwater choose to fly, and therefore their spatial distribution at sea. The intricate fine-scale dynamic soaring trajectory of the Manx Shearwater therefore impacts its coarse-scale movement patterns.
James Kempton
University of Oxford
Kempton, J.A., Wynn, J., Bond, S., Evry, J., Fayet, A.L., Gillies, N., Guilford, T., Kavelaars, M., Juarez-Martinez, I., Padget, O., Rutz, C., Shoji, A., Syposz, M. & Taylor, G.K.  2022.  Optimization of dynamic soaring in a flap-gliding seabird affects its large-scale distribution at sea. Science Advances, 8(22).  Open access: https://www.science.org/doi/10.1126/sciadv.abo0200<https://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2Fthe-soc.us12.list-manage.com%2Ftrack%2Fclick%3Fu%3D80f275938cdf39fdfc665205c%26id%3Dbc6eef27a8%26e%3D58dfde8d0a&data=05%7C01%7C%7Cc8f1cd094ed444a7b1e008dab1e4245d%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C638017890684410952%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=QH9yr5IZz70DGaJuN177OSXZ%2F%2BRifL3u3oNJH4X0f2E%3D&reserved=0>

May all your birds be identified,
Denis

Denis DeSilvis
Avnacrs 4 birds at outlook dot com

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