Alexander Wilson (1766-1813) was the first to document for science the Cerulean warbler (Plate 48). The taxonomic name that he gave the Cerulean warbler was Sylvia cærulea. Wilson was also the first to document for science the Blue-green warbler (Sylvia rara). Wilson discovered the bird “on the banks of Cumberland river.” Not wanting to exclude the bird from the first edition of Birds of America but not ever seeing or hearing a Blue-green warbler might have been the reason the bird that John James Audubon drew for the first edition of Birds of America looks a little too similar to the one that appears in Wilson’s American Ornithology (1808-1814).
For the later octavo edition of Birds of America, Audubon brought an end to the search for the Blue-green warbler. “As to the Sylvia rara [i.e. the Blue-green warbler], my doubts regarding its specific distinction from Sylvicola cærulea [i.e. the Cerulean warbler], are as great as ever, especially as no one has found its nest.” Audubon doubted the Blue-green warbler to the point where he dropped the bird altogether from the octavo edition. Furthermore, Audubon replaced the female Cerulean warbler that appears in the first edition with the drawing of the Blue-green warbler and titled it as a juvenile Cerulean warbler.