The Sibley-Monroe checklist was a landmark document in the study of birds conducted by Charles Sibley and Burt Monroe. It drew on extensive DNA-DNA hybridisation studies to reassess the relationships between modern birds.
The Sibley-Monroe assignment of individual species to families, and of families to orders remains controversial however. Critics maintain that while it marks a great leap forward so far as the evidence from DNA-DNA hybridisation goes, it pays insufficient attention to other forms of evidence, both molecular and on a larger scale. There is no true consensus but the broad middle-ground position is that the Sibley-Monroe classification, overall, is "about 80% correct". Research and debate concerning bird classification continue.
There are 9,994 species on the checklist, which is begun below and continues in several parts.