Harry Schelwald Swarth was born on January 26, 1878, in Chicago, Illinois.

He was an American ornithologist. In 1891, his family moved to Los Angeles. During his childhood, he was interested in birds and natural history and began collecting birds in 1894. He attended Baptist College in Los Angeles. In 1896, he joined the first extended natural history collecting expedition to Arizona. His book “A Distributed List of the Birds of Arizona” (1914) is recognized as the first attempt to catalogue all the birds of the state. He became a member of the Cooper Ornithological Club (now the Cooper Ornithological Society) in 1897. Swarth worked as an Assistant in the Department of Zoology at the Field Columbian Museum in Chicago, Illinois, from 1905 to 1908. In 1908, he returned to the West Coast to become an Assistant curator in Ornithology at the Museum of Vertebrate Zoology at the University of California Berkeley. In 1927, he became Curator of the Department of Ornithology and Mammalogy at the California Academy of Sciences. In 1930, he was elected to attend the 7th Annual International Ornithological Congress, held in Amsterdam, Holland. This allowed him to visit England, where he was received at the British and Rothschild Museums and conducted research that enabled him to complete the Avifauna of the Galapagos Islands, published in 1931. In 1932, he led the scientific staff of the Templeton Crocker Expedition of the California Academy of Sciences to the Galapagos Islands. Swarth was a member of the American Ornithologists' Union and the British Ornithologists' Union. He published more than 150 books and pamphlets on zoology.

In 1910, he married Winifern Wood (1885–1960). He died on October 22, 1935, in Berkeley, California.