Sibley's taxonomy has been a major influence on the sequences adopted by ornithological organizations, especially the American Ornithologists' Union.
Minor fields: Paleontology, Botany), he did his first fieldwork in Mexico in 1939 and 1941, then in Solomon Islands, Bismarck Archipelago, New Guinea, and the Philippines during World War II while on leave from the U.S. Navy, in which he was Ensign to Lieutenant in the Communications and Medical Service Corps.
By the early 1970s Sibley was pioneering DNA-DNA hybridisation studies, with the aim of discovering, once and for all, the true relationships between the modern orders of birds.
[1] With the passage of time and ever-improving laboratory methods, the balance of scientific opinion has shifted closer to the latter interpretation, though the picture is by no means clear-cut and simple.
His revised phylogeny of living birds in the light of DNA analysis, published in various forms in 1986–1993 was both controversial and highly influential.
[3]Partly due to personality conflicts, Sibley had few long-term collaborations with other scientists, with the notable exception of Jon Ahlquist.
There is some family resemblance, and Charles did a fair amount of genealogical research but could only establish that any relationship was no closer than fourth cousin.