Robert A. Gilbert (1870-1942) was an African-American naturalist and photographer, the long-time assistant to ornithologist William Brewster and a staff member of the MCZ. He was an Associate of the American Ornithologists' Union. The MCZ Archives holds some correspondence between Gilbert and Brewster, accessible through the Biodiversity Heritage Library.
More resources on Gilbert:
An obituary of Gilbert by MCZ curator Glover Allen in the Auk, (v. 59, p. 467, middle of the pdf file).
Thomas Barbour's report on the death of Gilbert in January 1942 and Allen's passing a few weeks later. (Annual Report of the MCZ 1941-42)
Ernst Mayr Library blog post from 2016, Notes from William Brewster: Trials in Wildlife Photography
A 2017 blog post from Audubon California, An Early Contributor to our Knowledge of Birds and Nature
John Hanson Mitchell's book, Looking for Mr. Gilbert : the Unlikely Life of the First African American Landscape Photographer (2014 e-book edition) or the original 2005 Looking for Mr. Gilbert: the Reimagined Life of an African American.