Les obseruations de plusieurs singularitez et choses memorables : trouuées en Grece, Asie, Judée, Egypte, Arabie ... en trois livres - Belon, Pierre, 1517? -1564 (Chez Guillaume Cauellat, 1554)

Observationes Zoologicae : quibus novae complures, aliaeque animalium species describuntur et illustrantur - Hermann, Johannis. (Amandum Koenig, 1804)

Observations in natural history : with an introduction on habits of observing, as connected with the study of that science ; also a calendar of periodic phenomena in natural history ; with remarks on the importance of such registers - Jenyns, Leonard, 1800 -1893 (John van Voorst, 1846)

Observations on the natural affinities that connect the orders and families of birds: togethers with description of a new species of scolopax ... with observations on the anas glocitans of pallas and a description of the female of that species - Vigors, N. A.‏ ‎ (Nicholas Aylward),‏ ‎ 1785 -1840 (Richard Taylor, 1825)

Occasional papers - Boston Society of Natural History. (1904)

Occasional papers of the Boston Society of Natural History - Boston Society of Natural History. (Boston Society of Natural History, 1904)

Occasional papers of the Museum of Natural History, the University of Kansas - University of Kansas. Museum of Natural History. (The University, 1989)

Occasional papers of the Museum of Zoology, University of Michigan - University of Michigan. Museum of Zoology. (University of Michigan, 1922)

Œuvres complètes de Buffon - Buffon, Georges Louis Leclerc, comte de, 1707 -1788 (Chez F.D. Pillot, 1831)

Œuvres complètes de Buffon avec la nomenclature Linnéenne et la classification de Cuvier - Buffon, Georges Louis Leclerc, comte de, 1707 -1788 (1853)

Of husbandry : in twelve books : and his book concerning trees - Columella, Lucius Junius Moderatus. (Printed for A. Millar, opposite to Catharine-street in the Strand, 1745)

Öfversigt af Kongl. Vetenskaps-akademiens forhandlingar - Kungl. Svenska vetenskapsakademien. (P. A. Norstedt & Söner, 1844)

Öfversigt af Kongl. Vetenskaps-akademiens forhandlingar - Kungl. Svenska vetenskapsakademien. (P. A. Norstedt & Söner, 1848)

Öfversigt af Kongl. Vetenskaps-akademiens forhandlingar - Kungl. Svenska vetenskapsakademien. (P. A. Norstedt & Söner, 1860)

Öfversigt af Kongl. Vetenskaps-akademiens forhandlingar - Kungl. Svenska vetenskapsakademien. (P. A. Norstedt & Söner, 1861)

Öfversigt af Kongl. Vetenskaps-akademiens forhandlingar - Kungl. Svenska vetenskapsakademien. (P. A. Norstedt & Söner, 1862)

Öfversigt af Kongl. Vetenskaps-akademiens forhandlingar - Kungl. Svenska vetenskapsakademien. (P. A. Norstedt & Söner, 1872)

Öfversigt af Kongl. Vetenskaps-akademiens forhandlingar - Kungl. Svenska vetenskapsakademien. (P. A. Norstedt & Söner, 1873)

Öfversigt af Kongl. Vetenskaps-akademiens forhandlingar - Kungl. Svenska vetenskapsakademien. (P. A. Norstedt & Söner, 1882)

Öfversigt af Kongl. Vetenskaps-akademiens forhandlingar - Kungl. Svenska vetenskapsakademien. (P. A. Norstedt & Söner, 1884)

L'Oiseau et la Revue francaise d'ornithologie - Société ornithologique de France. (Société ornithologique de France, 1934)

L'Oiseau et la Revue francaise d'ornithologie - Société ornithologique de France. (Société ornithologique de France, 1935)

L'Oiseau et la Revue francaise d'ornithologie - Société ornithologique de France. (Société ornithologique de France, 1936)

L'Oiseau et la Revue francaise d'ornithologie - Société ornithologique de France. (Société ornithologique de France, 1937)

L'Oiseau et la Revue francaise d'ornithologie - Société ornithologique de France. (Société ornithologique de France, 1939)

L'Oiseau et la Revue francaise d'ornithologie - Société ornithologique de France. (Société ornithologique de France, 1945)

L'Oiseau et la Revue francaise d'ornithologie - Société ornithologique de France. (Société ornithologique de France, 1960)

L'Oiseau et la Revue francaise d'ornithologie - Société ornithologique de France. (Société ornithologique de France, 1970)

Les Oiseaux d'Europe décrits par C. J. Temminck - Werner, Johann Carl. (1848)

Les oiseaux d'Europe, tableaux synoptiques - Paris, Paul, 1875 -1938. (L. Laveur, 1906)

Les oiseaux de l'est du Canada - Taverner, P. A. (Percy Algernon), 1875 -1947 (F.A. Acland, 1922)

Les oiseaux de l'Europe et leurs oeufs, décrits et dessinés dáprès nature - Dubois, Alphonse, 1839 -1921. (Chez C. Muquardt, 1872)

Les oiseaux de l'Europe et leurs oeufs, décrits et dessinés d'après nature - Dubois, Alphonse, 1839 -1921. (chez C. Muquardt, 1872)

Les oiseaux du Canada clef systématique pour l'identification des ordres, sous-ordres, tribus, familles, genres et espè ces - Provancher, L. (Léon), 1820 -1892 (s.n.], 1874)

Les oiseaux du Canada - Dionne, C.-E. (Charles-Eusèbe), 1846 -1925 (P. G. Delisle, 1883)

Les oiseaux du Canada - Dionne, C.-E. (Charles-Eusèbe), 1846 -1925 (s.n.], 1883)

Les oiseaux - Perrier, Edmond, 1844 -1921 (J.B. Bailli, 1904)

Oiseaux - Fédération des sociétés françaises de sciences naturelles. Office central de faunistique. (P. Lechevalier, 1921)

Okens Lehrbuch der Naturgeschichte - Oken, Lorenz, 1779 -1851 (Bei Carl Heinrich Reclam, 1815)

Okens Lehrbuch der Naturgeschichte - Oken, Lorenz, 1779 -1851 (Bei Carl Heinrich Reclam, 1816)

On the anatomy of vertebrates ... - Owen, Richard, 1804 -1892 (Longmans, Green and Co, 1866)

On the distribution of birds in Great Britain, during the nesting season - More, Alexander Goodman, 1830 -1895 (British Ornithologists' Union, 1865)

On the geology and natural history of the upper Missouri :Being the substance of a report made to Lieut. G.K. Warren, T.E. U.S.A - Hayden, F. V. (Ferdinand Vandeveer), 1829 -1887 (Printed by C. Sherman & son, 1862)

On the intestinal tract of birds; with remarks on the valuation and nomenclature of zoological characters - Mitchell, P. Chalmers Sir, (Peter Chalmers), 1864 -1945 (1901)

On the morphology of the duck and the auk tribes - Parker, William Kitchen William Kitchen Parker 1823 -1890 (s.n.], 1890)

On the natural history and classification of birds - Swainson, William, 1789 -1855 (John Taylor, 1836)

On the power, wisdom, and goodness of God : as manifested in the creation of animals, and in their history, habits, and instincts - Jones, Thomas Rymer, 1810 -1880 (H.G. Bohn, 1853)

On the power, wisdom and goodness of God, as manifested in the creation of animals, and in their history, habits and instincts - Kirby, William, 1759 -1850 (Carey, Lea & Blanchard, 1836)

On the power, wisdom and goodness of God as manifested in the creation of animals and in their history, habits and instincts - Kirby, William, 1759 -1850 (W. Pickering, 1835)

Onomasticon zoicon, plerorumque animalium differentias & nomina propria pluribus linguis exponens : cui accedunt Mantissa anatomica, et quaedam De variis fossilium generibus - Charleton, Walter, 1619 -1707 (Apud Jacobum Allestry ..., 1668)

The Oölogist for the student of birds, their nests and eggs - Lattin, Frank H. (Frank H. Lattin, 1915)

Oölogy of New England : a description of the eggs, nests, and breeding habits of the birds known to breed in New England, with colored illustrations of their eggs - Capen, Elwin A. (A. Mudge & son, printers, 1886)

Ootheca Wolleyana: an illustrated catalogue of the collection of birds' eggs - Newton, Alfred, 1829 -1907 (sold by R. H. Porter, 1905)

Ootheca Wolleyana: an illustrated catalogue of the collection of birds' eggs - Newton, Alfred, 1829 -1907 (sold by R. H. Porter, 1907)

Opera ornithologica - Bonaparte, Charles-Lucien, 1803 -1857 (1857)

Opinions and declarations rendered by the International Commission on Zoological Nomenclature - International Commission on Zoological Nomenclature (Printed by order of the International Trust for Zoological Nomenclature, 1956)

Opuscula ornithologica : notis et addendis, mss - Coues, Elliott, 1842 -1899 (1861)

The oriole : official organ of the Somerset Hills Bird Club - Somerset Hills Bird Club (Bernardsville, N.J.) (The Club, 1914)

Ornamental waterfowl: a practical manual on the acclimatization of the swimming birds - Hubbard, Rose E. (W. H. Robinson, 1907)

Ornis - International Ornithological Committee. (Carl Gerold's Sohn, 1885)

Ornis - International Ornithological Committee. (Carl Gerold's Sohn, 1886)

Ornis - International Ornithological Committee. (Carl Gerold's Sohn, 1887)

Ornis - International Ornithological Committee. (Carl Gerold's Sohn, 1888)

Ornis - International Ornithological Committee. (Carl Gerold's Sohn, 1890)

Ornis - International Ornithological Committee. (Carl Gerold's Sohn, 1891)

Ornis - International Ornithological Committee. (Carl Gerold's Sohn, 1895)

Ornis - International Ornithological Committee. (Carl Gerold's Sohn, 1896)

Ornis - International Ornithological Committee. (Carl Gerold's Sohn, 1898)

Ornis - International Ornithological Committee. (Carl Gerold's Sohn, 1899)

Ornis - International Ornithological Committee. (Carl Gerold's Sohn, 1910)

Ornis - International Ornithological Committee. (Carl Gerold's Sohn, 1905)

Ornithologia methodice digesta, atque iconibus aeneis ad vivum illuminatis ornata - Lorenzi, Lorenzo. (In Aedibus Mouchianis, 1767)

Ornithologia methodice digesta, atque iconibus aeneis ad vivum illuminatis ornata - Lorenzi, Lorenzo. (In Aedibus Mouchianis, 1769)

Ornithologia methodice digesta, atque iconibus aeneis ad vivum illuminatis ornata - Lorenzi, Lorenzo. (In Aedibus Mouchianis, 1776)

Ornithologia neerlandica. De vogels van Nederland - Oort, E. D. van (Eduard Daniël),‏ ‎ 1876 -1933 (M. Nijhoff, 1922)

Ornithologia, or, The birds: a poem, in two parts : with an introduction to their natural history; and copious notes - Jennings, James. (Sherwood, Gilbert, and Piper, 1829)