On Monday, February 24, 2020 at 10:33:46 PM UTC-6, John DeRosa OHM Ω http://aviation.derosaweb.net wrote:
https://youtu.be/2sh8_3-R90I

At 0:58 in the video the bird's wingtip vortices are described as "This helps provide lift". This statement caught my eye.

However, Wikipedia (https://en.wikipedia.org/wiki/Wingtip_device) mentions that "Wingtip devices increase the lift generated at the wingtip (by smoothing the airflow across the upper wing near the tip) and reduce the lift-induced drag caused by wingtip vortices, improving lift-to-drag ratio.

A contradiction?

- John non-aero-e DeRosa

There are always wing tip vortices when a wing is generating lift, but they can be tight and concentrated, like a horizontal tornado, or broad and diffuse. The tight and concentrated carry more energy that the diffuse vortices, even though the vorticity (and the generated lift) is the same.

Rich L