Why don't the pigeon hold the nest and do not hold it?

The pigeons may not hold the nest because the eggs may be white eggs, or they may be frightened, or the nest is passive.White eggs cannot be hatched.If they know that they are white eggs, they will not hatch again.If they are frightened by the outside world, they will also give up incubation.In addition, if the owners or others move their nests and let them notice it, they will not incubate again.