Response of breeding waders to agri-environmental schemes may be obscured by effects of existing hydrology and farming history

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 totanus 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 period 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.