Question 3.4

National indices are weighted when combined according to national population size estimates (from European Red List of Birds, BirdLife International 2021). Still, the quality of population estimates is very different between countries. Does it mean that weights are based on incorrect values?

Answer

Information on population size published by BirdLife International 2021 is the best source of information in Europe that is available (download here). There are indeed differences in the quality of information between countries. Still, the population estimates are robust, and to obtain extra guarantees, we asked the national coordinators to judge these estimates.