Port of Rotterdam is carrying out the Project Mainport Development Rotterdam, PMR, expanding the port with 1,000 hectares through suppletion of sand in the shallow coastal Voordelta area in the North Sea. As the Voordelta has the status of protected nature reserve (Natura2000 area), the loss of habitat, caused by the expansion of the port, must be compensated for. As part of the compensating measures, the Dutch national government established a series of protected areas in the Voordelta region and is following the effects of these measures. This dataset contains aerial counts of birds in the “Voordelta”. The set exists of a pre-protected status data (2003 – 2007) and a post-protected status (currently still under embargo).