• Richard Owen describes the mandible of the broad-billed parrot.
• Philip Sclater Exotic Ornithology (1866–69).
• Carl Jakob Sundevall Conspectus avium picinarum, Stockholm [Sweden] :Samson & Wallin, 1866.[on woodpeckers] online BHL
• Birds described in 1866 include Cabanis's tanager, bar-winged rail, spot-crowned antvireo, Van Dam's vanga, Mayotte drongo,
• Death of Johann Wilhelm von Müller
• Death of Philipp Franz von Siebold
• Axel Wilhelm Eriksson leaves Sweden for South-West Africa.
• Foundation of Museu Paraense Emílio Goeldi.
• Death of Christian Ludwig Landbeck. He had described many bird species in collaboration with Rodolfo Amando Philippi.
• Death of Ferdinand Joseph L'Herminier
• Philippi, R. A. & Landbeck, L. 1866. Beiträge zur Fauna Chiles. Archiv für Naturgeschichte 32: 121–132.Masafuera rayadito

Expeditions

• 1865–1868 Magenta circumnavigation of the globe Italian expedition that made important scientific observations in South America.

Ongoing events

• John Gould The birds of Australia; Supplement 1851–69. 1 vol. 81 plates; Artists: J. Gould and H. C. Richter; Lithographer: H. C. Richter
• John Gould The birds of Asia; 1850-83 7 vols. 530 plates, Artists: J. Gould, H. C. Richter, W. Hart and J. Wolf; Lithographers:H. C. Richter and W. Hart
• The Ibis