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.