Building homes on the water: a rescue mission for breeding birds

Breeding birds were in trouble on the Schellerwade, a beautiful arm of the IJssel River just west of Zwolle, Netherlands. The area has traditionally been a popular breeding destination for birds like the Black tern Chlidonias niger and the Mallard Anas platyrhynchos. However, the populations of both species have been declining, with the disappearance of grasses like crabgrass, used by Black terns as natural nesting habitat, and low chick survival rates for Mallards.

The A Rocha local group in Zwolle decided to take action. Each year, they prepare a series of floating nest rafts and lay them out in the Schellerwade, targeting the Black terns. The rafts were visible from the dike and were eagerly monitored to see if they would be used. In 2022 and 2023: no success. Disappointing, but this can happen with an opportunistic species like the Black tern. But in 2024, at least six of the nest rafts were occupied with young Black terns!  

This year, the team also placed five breeding baskets along the IJssel River, a new project focused on Mallards. The baskets stand on a framework of willow branches, protecting any eggs or chicks laid in the basket from predators. Last Saturday the team collected three of the baskets and determined that none had been used by nesting ducks. The remaining two are deeper in the reed bank, amidst dense vegetation, and will be collected later this year. The team will now consider why the nests weren’t used and what could be done differently – one hypothesis is that perhaps the baskets need to be placed further into the water. Next year, they’ll try again and hope for success!