It is not possible to give an exact figure that everybody would accept as
it varies from year to year, from one person's view to that of another, and
according to how you define 'species'. I have a Sibley & Monroe global
list (a few years old now) which has 9702 bird species, but the number will
have changed (probably increased - so you can think of 9700 as a rough
minimum figure) since it was published, with taxonomic revisions and the
discovery of a small number of new species. Moreover, this is using the
traditional Biological Species Concept. If you adopt an alternative way of
defining species, the Phylogenetic Species Concept, the total might be
closer to 30,000.
Birds Australia Conservation & Liaison,
Australian Bird Research Centre,
415 Riversdale Road,
Hawthorn East, VIC 3123, Australia.
Tel: (03) 9882 2622. Fax: (03) 9882 2677.
O/s: +61 3 9882 2622. Fax: +61 3 9882 2677.
Web Homepage: http://www.vicnet.net.au/~birdsaus/