Species and genera of Recent birds

29 p. ; 26 cm.Includes bibliographical references (p. 28-29)."Counts are presented for the numbers of species and genera of birds by orders and families to provide the data base for a comparative systematic analysis of the structure of the avian genus. These counts are based on the classification presented in the 'Reference list of birds of the world' and subsequent corrections. A total of 9021 species of birds exist in 2045 genera of which 3747 species in 941 genera are nonpasserine and 5274 species in 1104 genera are passerine. The species/genus ratio is calculated for each taxon with the average for all birds being 4.411 s/g. The distribution of genera of different size categories is tabulated for all birds and for selected subgroups. These distributions have the characteristic hollow-curve shape with a preponderance of small genera; 60.5 percent of all avian genera possess one or two species. The 39 largest genera are tabulated and analyzed; these comprise only 1.91 percent of all genera and contain 17.8 percent of all avian species or twice as many as in the one- and two-species genera. The possible reasons for the evolution of species-rich genera are outlined; the major ones are the ability of species in large genera to disperse and colonize new areas and the ability of these species to establish sympatry with congeneric species without divergence"--P. [1]