Natures wonders:seabird movement same in air and water (Introduction)

by David Turell , Wednesday, July 01, 2020, 20:06 (1604 days ago) @ David Turell

Evolved or designed, the seabird movements are analyzed:

https://www.sciencedaily.com/releases/2020/06/200630193211.htm

"New insight on how four species of seabirds have developed the ability to cruise through both air and water has been published today in the open-access journal eLife.

"The study reveals that these birds, from the Alcidae family which includes puffins, murres and their relatives, produce efficient propulsive wakes while flying and swimming. This means that the animals likely spend relatively low amounts of metabolic energy when creating the force they need to move in both air and water. The findings suggest that alcids have been optimised for movement in very different environments through the course of their evolution.

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"Lapsansky and his team tested whether alcids exhibit 'efficient Strouhal numbers' when flying in water and air. Animals move in these environments by using oscillating appendages. The Strouhal number describes the frequency at which an animal produces pulses of force with these appendages to power its movement. Only a narrow range of Strouhal numbers are efficient -- if a bird flaps its wings too fast or too slow, for a given amplitude and flight speed, then it wastes energy. But most birds have converged on this narrow range of Strouhal numbers, meaning that selection has tuned them to exhibit efficient flapping and swimming movements.

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"Their measurements showed that alcids cruise at Strouhal numbers between 0.10 and 0.40 in both air and water, similar to animals that stick to air or water only, but flap their wings approximately 50% slower in water. This suggests that the birds either contract their muscles at inefficient velocities or maintain a two-geared muscle system, highlighting a clear cost to using their wings for movement in air and water.

"'Our work provides detailed new insight into how evolution has shaped alcid flight in response to competing environmental demands in air and water," concludes senior author Bret Tobalske,"

Comment: Once these birds developed air and water movement, they could have adapted further. Originally they may have been designed.