Wetland criteria and birds in a changing delta

An assessment of the changes in the ornithological value of the delta area in the southwestern part of The Netherlands was made, based on the criteria and standards of Szijj, by comparing data derived from bird counts made before the implementation of the delta project with those made after the closure of two estuaries and with the estimated numbers of birds for three possible future infrastructural models.It appears that all the sites examined are, and will remain, of international ornithological importance.Owing to their different environmental character each individual basin of the delta area can be considered as an internationally important wetland.As a result of the delta works, different types of habitat and management of the basins will have to be chosen so that a species of a group of species may be given priority.To justify the choice, fixed target numbers of the populations and a sound knowledge of the availability of suitable habitats is needed. A number of questions arose about the selection of sites and the possibility of conserving wetlands such as those in the delta area. Further development of the criteria and standards of Szijj and more uniform application is advocated.