ORIGINAL ARTICLE Response of breeding waders to agri-environmental schemes may be obscured by effects of existing hydrology and farming history Johnny Kahlert Æ Preben Clausen Æ Jens Peder Hounisen Æ Ib Krag Petersen Received: 30 October 2006 / Revised: 18 January 2007 / Accepted: 13 June 2007 / Published online: 20 July 2007 Ó Dt. Ornithologen-Gesellschaft e.V. 2007 Abstract The initiation of agri-environmental schemes (AES) to improve habitats for breeding waders may not show expected benefits in all situations. We show this, using results from a study of breeding waders on 469 grassland fields in the Danish Wadden Sea area. Numbers of breeding waders were not restored to levels of the recent past, even though Lapwings Vanellus vanellus, Black- tailed Godwits Limosa limosa and Redshanks Tringa tot- anus were drawn to wet permanent grasslands with AES. We had expected that more waders would be attracted by improved surface water retention during the breeding per- iod due to the AES. However, AES were not introduced to all fields, and this measure did not dramatically change the water regime in part of the breeding fields. Furthermore, dry grasslands and fields that had been cultivated or drained before did not attract more waders, despite the introduction of the AES. The results suggest that the interplay between surface water retention and former farming history are important determinants of the habitat choice for breeding waders. The study emphasises the need for pre-defined success criteria, thorough analysis of the nature of the habitat and consideration of population processes before initiation of an AES, so that realistic management goals are defined and expected benefits can be achieved. Keywords Cultivation Á Draining Á Meadow birds Á Sustainable agriculture Á Wetness Introduction In Western Europe, habitats of waders breeding in farm- land have changed dramatically. Grassland has reverted to tall grass and shrub (Weis 2001; Ottvall and Smith 2006) and farming practice was markedly intensified (e.g. Krebs et al. 1999; Donald et al. 2001). According to Newton (2004), it is likely that these changes have caused the se- vere decline in farmland bird numbers observed in recent decades, probably as a result of insufficient reproductive success. In order to reverse this negative trend, agri-environ- mental schemes (AES) have been introduced in many countries. These schemes vary greatly with respect to target species, prescriptions and uptake rate, and in the efficiency of creating better conditions for target species (Kleijn and Sutherland 2003). On a landscape scale, AES may involve measures to optimise hydrological conditions as well as prescriptions on farming activities, e.g. restrictions on grazing and use of pesticides or delayed mowing (Beinte- ma and Mu ¨skens 1987; Kleijn et al. 2001, 2004). Elevated ground water levels or the presence of surface water in fields has generally been found to stimulate the settlement of breeding waders or the foraging efficiency of adults or chicks (O’Brien and Self 1994; Johansson and Blomquist 1996; Ausden et al. 2001; Milsom et al. 2002; Kleijn and van Zuijlen 2004; Smart et al. 2006). The importance of water may not be surprising, as wet grass- land is generally considered as a stronghold for waders compared to arable land, where several species are unlikely to breed, or if breeding, do so at low densities or with low success (e.g. Berg et al. 1992; Salek and Smilauer 2002; Ratcliffe et al. 2005; Gunnarsson et al. 2006). Conversion of arable land into wet grassland is an element of AES in many European countries, although it may serve functions Communicated by F. Bairlein. J. Kahlert (&) Á P. Clausen Á J. P. Hounisen Á I. K. Petersen Department of Wildlife Ecology and Biodiversity, National Environmental Research Institute, A ˚ rhus University, Grena ˚vej 14, Rønde 8410, Denmark e-mail: jok@dmu.dk 123 J Ornithol (2007) 148 (Suppl 2):S287–S293 DOI 10.1007/s10336-007-0181-x