Which bird thermals the best?

Martin Gregorie wrote:
About the best I've watched are kites - both the Indian Brown Kites and
the Red Kite that are now spreading across the UK.

I can't judge it, but I've heard that if there are Swifts, they are
pretty reliably in the core of the thermal (because their food is there).

The other top birds IMO are storks. I was flying models at a major

Not surprizingly, Otto Lilienthal spent a lot of time watching storks.