How many species of birds are there?

How to get close to this number

Use the comparisons in the explanation as your scale. Mammals number in the thousands and described insects in the millions; birds are far more diverse than mammals and nowhere near insects. That places them in the low tens of thousands, and knowing the neighbours of a category is usually a better guide than trying to recall the category itself.

The count is genuinely unstable, and for an interesting reason. Genetic work keeps revealing that what looked like one species is several, or that two named species interbreed and are one — so the total moves as taxonomy is revised rather than as birds appear or vanish. Different authorities publish different totals at the same moment, which is why the question names a specific list.

The conservation figure in the explanation is the one worth carrying away: roughly one species in eight is threatened. That proportion is what makes the total count matter, because a diversity figure only means something alongside a trajectory. Species counts are also biased by attention — well-studied regions yield more recognised species than poorly surveyed ones, which is a limitation of the data rather than of the birds.