The article discusses the development of indicators for measuring biodiversity, focusing on European birds as a case study. The authors highlight the global commitment to reduce biodiversity loss by 2010 and the need for robust indicators to assess progress. They propose a classification of biodiversity indicators and present methods to construct and interpret these indicators using population data from national breeding bird surveys in Europe. The indicators are designed to measure trends in bird populations, with a focus on common farmland and woodland birds. The results show that common farmland birds have declined significantly over the last two decades, while woodland birds have remained stable. The decline in farmland birds is attributed to increased agricultural intensification. The authors argue that the farmland bird indicator can serve as a useful surrogate for trends in other elements of biodiversity in this habitat. The article also discusses the strengths and weaknesses of the European wild bird indicator, emphasizing the importance of species selection, data quality, and statistical methods in constructing reliable indicators.The article discusses the development of indicators for measuring biodiversity, focusing on European birds as a case study. The authors highlight the global commitment to reduce biodiversity loss by 2010 and the need for robust indicators to assess progress. They propose a classification of biodiversity indicators and present methods to construct and interpret these indicators using population data from national breeding bird surveys in Europe. The indicators are designed to measure trends in bird populations, with a focus on common farmland and woodland birds. The results show that common farmland birds have declined significantly over the last two decades, while woodland birds have remained stable. The decline in farmland birds is attributed to increased agricultural intensification. The authors argue that the farmland bird indicator can serve as a useful surrogate for trends in other elements of biodiversity in this habitat. The article also discusses the strengths and weaknesses of the European wild bird indicator, emphasizing the importance of species selection, data quality, and statistical methods in constructing reliable indicators.