A family tree covering all the 9,993 known species has been unveiled in the journal Nature after three years of work.
This is not going to solve arguments over just how many species there are, how many of those described are valid, or even how to classify them - bird classification is a cauldron of conflicting theories, modern DNA tools notwithstanding. But this massive effort has given us our best idea ever of how birds evolve and form new species. Some lineages produce species faster than others, but ornithologists were surprised by the steadiness of bird speciation, averaging 0.74 species every mission years. Most classes tail off in the rate of new species formation: Aves does not, perhaps because of birds' abilities to colonize new ranges more effectively than ground-bound species.
So, birdwatchers, get to work!