For the history of the classification of birds see the article Ornithology, where also the more important ornithological works are mentioned.
The HoLARCTIC Region, comprising North America and the extratropical mass of land of the Old World, may from an ornithological point of view be characterized by the Colymbi, Alcidae, Gallidae or Alectoropodous Galli, and the Oscines, which have here reached their highest development; while Ratitae, Tinami, Psittaci, and non-Oscine Passeres (with the exception of Tyrannidae extending into North America and Conurus carolinensis) are absent.
This elastic application renders it impossible in the following sketch of the history of ornithology to draw any sharp distinction between works that are emphatically ornithological and_those to which that title can only be attached by courtesy; for, since birds have always attracted far greater attention than any other group of animals with which in number or in importance they can be compared, there has grown up concerning them a literature of corresponding magnitude and of the widest range, extending from the recondite and laborious investigations of the morphologist and anatomist to the casual observations of the sportsman or the schoolboy.
Sundevall - equally proficient in classical as in ornithological knowledge - was, in 1863, compelled to leave more than a score of the birds of which Aristotle wrote unidentified.
Ment, especially as a new edition was called for in 1790, the ornithological portion of which was begun by Bonnaterre, who, however, had only finished three hundred and twenty pages of it when he lost his life in the French Revolution; and the work thus arrested was continued by Vieillot under the slightly changed title of Tableau encyclopedique et methodique des trois regnes de la Nature - the Ornithologie forming volumes four to seven, and not completed till 1823.
How would you define ornithological? Add your definition here.