In 1948-49, he was accompanied by Dr. Phillip Clancey on an ornithological expedition to Arabia, Yemen, Aden, Somalia, Ethiopia, Kenya, and South Africa. As the author of numerous taxonomic and other works on birds, and possessing a vast collection of bird and bird lice specimens, he was long considered one of Britain's greatest ornithologists. Garfield, however, claims Meinhertzhagen's magnum opus, Birds of Arabia (1954), was based on the unpublished manuscript of another naturalist, George Bates, who has been insufficiently credited in the work.