What do birds tell us about recent changes in the environment?
The loss of biodiversity has become an increasingly important topic of societal discussions. However, measuring biodiversity loss is not easy compared to for instance documenting the other environmental crisis, the climate change. Therefore, different tools are needed to measure whether biodiversity has changed, and how it reflects known habitat changes and possible conservation actions. Birds have been used in many countries as indicators of environmental status. There are several reasons for this. There is a large number of bird enthusiasts around the world who collect data on species. This has led to the accumulation of a considerable amount of long-term data on birds, and the amount of data is increasing every year. Because birds are at the top of the food chain, which means that their numbers are likely to reflect changes at lower trophic levels. Birds are also ubiquitous in a variety of environments and every human knows something about birds, which greatly facilitates the popularisation of science and communication of the impacts of habitat change.