Common birds in Europe — population index (1980 = 100)

For common farmland bird species, n = 36; for common forest bird species, n = 29; for all common bird species (this line includes the farmland and forest birds as well as other common species that are not primarily associated with either of these habitats), n = 135. Country coverage (i.e. reflecting the availability of high-quality monitoring data from annually-operated common bird monitoring schemes, employing generic survey methods and producing reliable national trends): Austria, Belgium, Bulgaria, Czech Republic, Denmark, Estonia, France, Finland, Germany, Hungary, Ireland, Italy, Latvia, the Netherlands, Norway, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom. See www.ebcc.info for more technical information on the calculation of the index. It should be underlined that the methodology for calculating the farmland bird index has recently changed. The new index presents a much sharper drop around the years of 1995 and 1996. While the new index is recognised as integrating better expertise in terms of species selection, further investigation is necessary to explore what is behind this drop. In addition, the influence of including both new species and the new Member States in the selection, and the starting year of monitoring schemes in some countries should be further investigated. In any case, the trend from 1996 onwards is consistent with the previous methodology and shows the index to be fairly stable.