Nesting habitat selection by bitterns Botaurus stellaris in Britain and the implications for wetland management

The rarity and decline of the bittern Botaurus stellaris in Britain has prompted large-scale wetland restoration and more recently, wetland creation projects. In order to guide such habitat management, we investigated whether any large or fine-scale features within British wetland sites best described the selection of female bittern nesting positions. Birds nested in continuous vegetation (usually Phragmites dominated) that was on average 100 m at its narrowest width. When compared with random locations, nests had less scrub and more vegetated open water edge in their wider vicinity and were immediately surrounded by smaller percentage coverage of non-Phragmites species and thicker Phragmites stems. Of most importance, female bitterns nested at points where deeper water was maintained into the driest part of the season, perhaps using the presence of water tolerant plant species as an indication of this. The results can be used to aid the design of new wetland sites to take into account the needs of nesting female bittern.