Olson's work in Panama attracted the attention of
Alexander Wetmore in 1967, as Wetmore was preparing a
monograph on Panama bird life. Their contact at the
National Museum of Natural History (NMNH)—administered by the
Smithsonian—earned Olson a summer job in the
Fish and Wildlife Service under
Richard C. Banks the next year. This work was the basis of his
dissertation on the evolution of
rails. Johns Hopkins would award Olson an
Sc.D. in 1972. By August 1971 he was working at the NMNH on a predoctoral fellowship. He wrote on fossil rails for a 1977 monograph by
Sidney Dillon Ripley. In March 1975, he was made
curator of the Division of Birds. In 1976 he met his future wife
Helen F. James who later became another notable paleornithologist herself, focusing on
Late Quaternary prehistoric birds. During their pioneering research work on Hawaii, which lasted 23 years, Olson and James found and described the remains of 50 extinct bird species new to science, including the
nēnē-nui, the
moa-nalos, the
apteribises, and the
Grallistrix "
stilt-owls". He was also one of the authors of the description of the extinct rodent
Noronhomys vespuccii. In 1982, he discovered subfossil bones of the long ignored
Brace's emerald on the
Bahamas, which gave evidence that this hummingbird is a valid and distinct species. In November 1999, Olson wrote an open letter to the
National Geographic Society, in which he criticized Christopher P. Sloan's claims about the dinosaur-to-bird transition which referred to the fake species "
Archaeoraptor". In 2000, he helped to resolve the mystery of
Necropsar leguati from the
World Museum Liverpool, which turned out to be an
albinistic specimen of the
grey trembler. ==Personal life==