Giant Butterbur (Petasites japonicus), also known as Sweet Colt's-foot or Fuki, is a robust herbaceous perennial in the Butterweed tribe (Senecioneae) of the Daisy Family (Asteraceae), native to China, Japan, Korea, Sakhalin, and the Russian Far East. The inflorescences emerge first in Spring, followed by the large leaves that persist through Summer before dying back in the Fall. There are a number of other Colt's-Foot (Petasites spp.), but Petasites japonicus has larger leaves than most. Most Petasites are native to Eurasia, and nearby islands such as Great Britain, Ireland, Japan, Sakhalin, and Taiwan. One species (P. pyrenaicus) extends into Algeria and Tunisia, and some forms of Arctic Butterbur (P. frigidus) are common in Canada, Alaska, and the northern half of the U.S.
The leaves themselves do not capture and hold water, so would not serve as a bird-bath. However, I imagine the graceful form of the leaves could serve as a design inspiration for bird-baths constructed of some other material, such as metal, glass, ceramics, etc.