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.
These detailed statistics allow effective monitoring of the environment. This is because birds are an indicator species of how well the ecosystem is functioning to provide food, clean water, good soil and quality of life for people.
