According to experts, about 50 billion birds live in the world. Thus, there are on average six birds for each person, writes Popular Mechanics. These fifty billion include 9,7 thousand bird species: from the stylobeak to the zebra finch.

Note that the published data has been combined with real case studies and a scaling algorithm. All this was necessary for a correct assessment of the number of birds on the planet as a whole.

Interestingly, there are very few bird species left on Earth. For example, the population of black-breasted quail is only about 100 birds.