A large area of reclaimed land with meadows along the Vidåen river. In the western part a saltwater lagoon is maintained by pumping in seawater. The inner (eastern) parts are mainly agricultural and the outer (western) parts predominantly pasture. There is also some standing freshwater, notably Rudbøl Sø, and reedbeds.
This is a very important staging area for several waterbirds, with total numbers exceeding 20,000 individuals. Several species listed on Annex I of the EC Birds Directive breed at the site, including Botaurus stellaris, Ciconia ciconia, Circus aeruginosus, Circus pygargus, Porzana porzana, Recurvirostra avosetta, Sterna hirundo, S. paradisaea, S. albifrons,Chlidonias niger (the most important site in Denmark for this species) and Luscinia svevica.
National Partial International High6,520 ha of IBA covered by Special Protection Area (Vidåen, Tøndermarsken and Saltvandsøen, 6,520 ha).
BirdLife International (2019) Important Bird Areas factsheet: Tøndermarsken, Magisterkog and Rudbøl Sø. Downloaded from
http://www.birdlife.org on 23/05/2019.