Experimental Manipulation of Water Table and Grazing Pressure as a Tool for Developing and Maintaining Habitat Diversity for Waterbirds

Abstract

The relationship between reed Phragmites australis cover of ditches and habitat use by marshland birds was studied in an experimental area of the Oostvaardersplassen nature reserve in The Netherlands. Water table and grazing by cattle and horses had an important impact on the development of P. australis in ditches and pools, resulting in three different types of habitat: deep open water, shallow open water and shallow water with P. australis vegetation. Shallow water bodies with a reed cover of less than 10% were most frequently visited by foraging Eurasian Spoonbill Platalea leucorodia, Smew Mergellus albellus, herons, ducks, waders and rails. Breeding grebes and marshland passerines, however, preferred parts with more reed cover. It is concluded that the creation of shallow water bodies, together with adjusted water table management and grazing pressure are suitable tools for restoring habitats preferred by marshland birds.