These items are hand-blown art glass swan bowls, which were popular Mid-Century Modern collectibles used as decorative centerpieces, candy dishes!
Who Made Them?
The vast majority of this specific stylecharacterized by a long curved neck, heavily marbled colors, and dramatic ruffled or scalloped wing edgeswere actually made in the United States (specifically Oklahoma, Arkansas, and the surrounding Ozark region) from the late 1950s through the 1970s.
They are collectively and generically known as "Sooner Glass" (named after Oklahoma's nickname, the Sooner State) or "Arklahoma Art Glass".