A furious protest from pigeon owners ensued – there were more than 25,000 in the Netherlands – and this seemed to help. The German occupier adjusted the measure. Pigeons were simply prohibited from flying and had to be registered. A special police unit, the so-called Duivenbrigade (Dove Brigade), was established to enforce this: free flying pigeons were shot down. But the measure proved to be untenable. So as of August 1942 all of these bird owners were still required to put an end to their prized pigeons. As proof of compliance, they had to submit the chopped off feet of their birds to the local authorities.