Robert Bruce Horsfall (1869-1948) was an American wildlife illustrator. His paintings were included in several works from the early 20th century, including Frank M. Chapman's Warblers of North America.
American land birds by Alice E. Ball ; illustrated by Robert Bruce Horsfall. (1936) New York : Tudor, 1936.
Bird and animal paintings, by R. Bruce Horsfall; text by Carra E. Horsfall. Washington, D.C., Nature magazine 
Birds of California : an introduction to more than three hundred common birds of the state and adjacent islands, with a supplementary list of rare migrants, accidental visitants, and hypothetical subspecies by Irene Grosvenor Wheelock ; with ten full-page plates and seventy-eight drawings in the text by Bruce Horsfall. Chicago : A.C. McClurg, 1912, c1903.
Birds of North Carolina, by Thomas Gilbert Pearson, Clement Samuel Brimley and Herbert Hutchinson Brimley, illustrations by Rex Brasher, Robert Bruce Horsfall, and Roger Tory Peterson. North Carolina Department of Agriculture, State Museum Division. Raleigh, Bynum Printing Company, 1942.
Birds of the Pacific Coast, by Willard Ayres Eliot, including a brief account of the distribution and habitat of one hundred and eighteen birds that are more or less common to the Pacific Coast states and British Columbia w/ 56 color plates by R. Bruce Horsfall. New York : G.P. Putnum's Sons, 1923
Familiar birds of the Northwest : covering birds commonly found in Oregon, Washington, Idaho, northern California and western Canada by Harry B. Nehls ; with paintings by R. Bruce Horsfall ... [et al.]. Portland, Or. : Portland Audubon Society, c1981.
A year with the birds by Alice E. Ball ; illustrated by Robert Bruce Horsfall. New York : Gibbs & Van Vleck, 1916, 1917.