In the middle of the nineteenth century, the Canadian physician and naturalist Alexander Milton Ross became a supporter of the Underground Railroad, a system of contacts and safe houses that helped fugitive slaves in the United States of America escape their captors, finding freedom in the Northern States or in Canada. 
Following his medical studies, Ross travelled through the United States and Canada assisting Railroad activities. In the southern states, he worked incognito, posing as an ornithologist (which earned him the nickname 'The Birdman') and held secret meetings with enslaved people where he provided information and supplies to assist their escape. Settling in Toronto in 1865, he published two memoirs recounting his life as an abolitionist.
Much of the information on Ross's life during this period comes from these autobiographies so his achievements must be treated with caution, although evidence from letters and the testimony of others lend veracity to the accounts. The books describe acquaintances with several prominent abolitionists as well as the American President, Abraham Lincoln (for whom he acted as a secret agent during the American Civil War), Giuseppe Garibaldi and the Mexican President, Benito Juarez. 
In later life, Ross pursued his interests in natural history and made important contributions to the study of Canadian flora and fauna. He identifed and classified over 500 species of Canadian migratory birds, 200 species of mammals and fish, 3400 species of insect and 2000 plants. However, he was also criticised for his staunch opposition to vaccination during the Toronto smallpox epidemic in 1885, despite evidence that he himself had been inoculated.