Pest control companies rounded up and gassed almost 7,000 geese in a 20 kilometre radius from Amsterdam’s Schiphol airport this spring, the NRC reports on Monday.

This is down some 3,000 on the same period in 2013. Arie den Hertog, who is in charge of the infrastructure ministry’s efforts to reduce the danger to aircraft caused by the geese, says the lower catch reflects the success of the project.

Nevertheless, bird migration experts say gassing the geese is not a long-term solution. ‘Within two years, population levels will be restored,’ researcher Julia Stahl told the NRC.

The lack of competition for food and good nesting places will encourage birds from elsewhere in the Netherlands to move to the area around Schiphol, she said.

Reseachers say changing crops and farming methods offer a better solution.