This year, the 56 females averaged 2.6 eggs. This corresponds to the long-term average. If this value were exceeded in several consecutive years, this would be an alarm signal that there is too little food (fish).
We also checked eggs for toxins in the past. It turned out that in the 1990s the concentration of PCB was too high. From heavily loaded eggs no chicks hatched. Although the PCB levels are still high, they are no longer critical.
We have not been able to determine egg predation in Birgelfeld so far. Egg predators have no chance on the rafts against the attacking terns.