How many species of birds have existed?

The Pleistocene avifauna of Arredondo, Florida.
by: Brodkorb, Pierce, 1908-1992
Published: (1959)

The age of birds /
by: Feduccia, Alan
Published: (1980)

Relationships in the Charadrii (shorebirds) : a taxonomic study based on color patterns of the downy young /
by: Jehl, Joseph R.
Published: (1968)

The wing of Titanis walleri (Aves:Phorusrhacidae) from the late Blancan of Florida /
by: Chandler, Robert M.
Published: (1994)

Relationships and evolution of flamingos (Aves, Phoenicopteridae) /
by: Olson, Storrs L.
Published: (1980)

Paleognathous birds from the early Tertiary of the northern hemisphere /
by: Houde, Peter W.
Published: (1988)

Breeding birds in a Florida suburb /
by: Woolfenden, Glen Everett, 1930-, et al.
Published: (1969)

Measurements of birds /
by: Baldwin, S. Prentiss (Samuel Prentiss), 1868-1938, et al.
Published: (1931)

Two mid-Pleistocene avifaunas from Coleman, Florida /
by: Ritchie, Thomas L.
Published: (1980)

Birds of Canada /
by: Taverner, P. A. (Percy Algernon), 1875-1947
Published: (1934)

The birds of Canada /
by: Godfrey, W. Earl
Published: (1966)

A comparative study of bird populations in Illinois, 1906-1909 and 1956-1958 /
by: Graber, Richard Rex
Published: (1963)

The breeding birds of Kansas /
by: Johnston, Richard F.
Published: (1964)

World bird species checklist : with alternative English and scientific names /
by: Wells, M. G. (Mic G.)
Published: (1998)

Observations on some Wyoming birds /
by: Fuller, Arthur Bennett, 1893-

Bird families of the world /
Published: (1978)

The birds of the Santa Marta region of Colombia : a study in altitudinal distribution /
by: Todd, W. E. Clyde (Walter Edmond Clyde), 1874-1969
Published: (1922)

Birds of Western Canada /
by: Taverner, P. A. (Percy Algernon), 1875-1947
Published: (1928)

Birds of eastern Newfoundland /
by: Aldrich, John Warren
Published: (1939)

Physiology of the temperature of birds /
by: Baldwin, S. Prentiss (Samuel Prentiss), 1868-1938
Published: (1932)

Birds--their life, their ways, their world /
Published: (1979)

Notes on summer birds of the northwestern parishes of Louisiana /
by: Strecker, John Kern, 1875-1933
Published: (1928)

A quantitative study of the nocturnal migration of birds.
by: Lowery, George H., Jr., 1913-1978
Published: (1951)

The birds of Costa Rica : distribution and ecology.
by: Slud, Paul
Published: (1964)

Birds from Coahuila, Mexico.
by: Urban, Emil K.
Published: (1959)

Birds from North Borneo /
by: Thompson, Max C.
Published: (1966)

The distribution of birds in Venezuelan páramos /
by: Vuilleumier, François, 1938-
Published: (1978)

Descriptions of new birds from Oregon : chiefly from the Warner Valley region /
by: Oberholser, Harry C. (Harry Church), 1870-1963
Published: (1932)

Birds of the Niagara frontier region : an annotated checklist /
by: Beardslee, Clark Smith, 1898-1957
Published: (1965)

The origin and evolution of birds /
by: Feduccia, Alan
Published: (1996)

The rise of birds : 225 million years of evolution /
by: Chatterjee, Sankar
Published: (1997)

The rise of birds : 225 million years of evolution.
by: Chatterjee, Sankar
Published: (2015)

The birds of the Belgian Congo /
by: Chapin, James Paul, 1889-
Published: (1932)

Birds and nature.
Published: (1900)

A hand-list of the genera & species of birds : <Nomenclator avium tum fossilium tum viventium> /

Summer birds from the Yucatan Peninsula, Mexico /
by: Klaas, Erwin E.
Published: (1968)