In 1892, Grönvold left for America by way of England. It was in London that he landed a job preparing bird skeletons for the Natural History Museum. There he developed skill as a taxidermist and established his reputation as an artist. In 1895, Grönvold joined an expedition to the Savage islands, returning later to continue as an artist at the Museum.
By the end of the century, Grönvold’s work was well represented in the scientific literature. Grönvold also completed numerous plates for Lord Rothschild. He also produced plates of bird eggs, which were quite unusual and rarely found in early bird books.