If you use this type of nest this trick can be useful.
Last year, a male regularly messed up or removed nest materials. Certainly with the aim of starting another brood.
The bottom of these nests being flat, the eggs were found scattered and therefore a risk of not being incubated was very possible.
So I looked for a solution to avoid this inconvenience. By trying out several types of concave shaped nest bottom, among others those in rope and coconut fiber, by incorporating them into the plastic nest. This male continued despite everything to want to remove these funds !
Then, I tried a white felt concave background that I taped to the nest.