a1 European Bird Census Council and The Royal Society for the Protection of Birds, The Lodge, Sandy, Bedfordshire SG19 2DL, U.K.
a2 Czech Society for Ornithology, Na Bělidle 252/34, CZ-150 00 Prague 5, Czech Republic
a3 British Trust for Ornithology, The Nunnery, Thetford, Norfolk, IP24 2PU, U.K.
a4 Statistics Netherlands, PO Box 4000, 2270 JM Voorburg, the Netherlands
a5 The Royal Society for the Protection of Birds, The Lodge, Sandy, Bedfordshire SG19 2DL, U.K.
a6 SOVON, Dutch Centre for Field Ornithology, Rijksstraatweg 178, 6573 DG, Beek-Ubbergen, the Netherlands
a7 BirdLife International, Wellbrook Court, Girton Road, Cambridge CB3 0NA, U.K.
Global and regional targets to reduce the rate of biodiversity loss bring with them the need to measure the state of nature and how it is changing. A number of different biodiversity indicators have been developed in response and here we consider bird population indicators in Europe. Birds are often used as surrogates for other elements of biodiversity because they are so well known and well studied, and not for their unique intrinsic value as environmental indicators. Yet, in certain situations and at particular scales, trends in bird populations correlate with those of other taxa making them a valuable biodiversity indicator with appropriate caveats. In this paper, we look at two case studies, in the UK and Europe as a whole, where headline bird indicators, that is, summary statistics based on bird population trends, have been developed and used to inform and assist policy makers. Wild bird indicators have been adopted by many European countries and by the European Union as indicators of biodiversity and of sustainable development. In the discussion, we review the strengths and weaknesses of using bird populations in this way, and look forward to how this work might be developed and expanded.