Does flying while polymorphed into a flying creature count as flying by magical means for the purposes of blizzards?

Icewind Dale is a nasty place, where blizzards frequently turn the frozen wastes into an untraversable nightmare. One of the rules for blizzards included in Icewind Dale: Rime of the Frostmaiden makes flying nearly impossible:

The wind extinguishes open flames, disperses fog, erases tracks in the snow, and makes flying by nonmagical means nearly impossible. A creature falls at the end of its turn if it is flying by nonmagical means and can’t hover.

Suppose I use polymorph to change into a giant eagle. Does flying as this giant eagle count as flying by magical means?