Robert A. Gilbert

During the 1890s Brewster was transitioning from collecting bird specimens with a shotgun to documenting wildlife by field observation and photography, and Gilbert — already knowledgeable in ornithology and skilled in photographic processing — became a key collaborator. Inscriptions on the reverse of surviving prints indicate that Gilbert owned darkroom equipment and produced prints from glass plate negatives. The full extent of Gilbert's photographic output is unclear because most images in the collection were attributed by default to Brewster. Of more than 1,700 photographic prints in the Ernst Mayr Library of the MCZ, only six bear verso inscriptions explicitly identifying Gilbert as the photographer, including views of a wood-shed at Hemlock Grove in Concord (April 1904) and of Brewster's garden in Cambridge (July 1904). Scholars have suggested that many additional photographs in the collection may be Gilbert's work, and a cooperative research project between the Ernst Mayr Library and the Museum of American Bird Art at Mass Audubon is examining Brewster's digitized journals and diaries to clarify Gilbert's role. The rediscovery of Gilbert's photographic contributions began in the mid-1970s, when author John Hanson Mitchell — then editor of Mass Audubon's Sanctuary magazine — found more than 2,000 of Brewster's glass plate negatives in the attic of a Massachusetts Audubon Society building. One image, depicting a young Black man in front of a rustic cabin, prompted Mitchell to investigate the subject's identity; he was later told by an MCZ archives assistant that the photographs had likely been taken by Brewster's assistant, Robert Gilbert. Mitchell's research culminated in the 2005 book Looking for Mr. Gilbert: The Reimagined Life of an African American, reissued in 2014 as Looking for Mr. Gilbert: The Unlikely Life of the First African American Landscape Photographer.

Gilbert died on January 7, 1942, in Cambridge, Massachusetts. In the MCZ Annual Report for 1941–1942, director Thomas Barbour wrote a tribute describing Gilbert's "sterling personal characters of integrity, affection, courtesy, and loyalty." Gilbert's contributions received renewed institutional recognition in the twenty-first century. In 2022, the Concord Museum and Mass Audubon mounted the exhibition Alive with Birds: William Brewster in Concord, which highlighted Gilbert's role as Brewster's longtime assistant and as an ornithologist and photographer in his own right. The Ernst Mayr Library has also undertaken digitization and transcription of Brewster's journals and diaries in part to clarify the scope of Gilbert's photographic and scientific contributions.