It is well known phenomenon when white storks (Ciconia ciconia) - as well as other big birds – can fly a long distances almost without flopping by wings. It is because they can quickly find and use the warm slopes of air and flying up quite easy, then moving by planning flight slowly down to another `thermal air flow` and so on.
07-08-2022, Hrodna region in W Belarus
Several pictures and long read in Belarusian here:
Вялікі тэкст і некалькі здымкаў пра белых буслоў і наша смецце тут: