If you live in Europe, you can find almost any statistic you like about the birds in the environment. How many there are of a species, where you find them, whether their population is increasing or decreasing. In some countries like the UK there are comprehensive surveys going back 60 years and they have mapped and counted every single bird species three times already.
Click here for original story, We’ve been tracking birds in a small Nigerian forest for 18 years—what we found and why it matters
Source: Phys.org