China outdoor composite wall cladding and pigeon in our Home wall. There is a pigeon in our home wood wall board made a nest, my children see very happy, always go to the window to see the pigeon, pigeon later gave birth to three eggs, three eggs were hatched the little pigeon, children see little pigeon very happy, took me occasionally go to see the little pigeon, slowly learned to fly, but this time the wooden wall board pigeon nest old pigeon eggs, after a few days, the old pigeon and three little pigeon flew away, but the eggs in the bird's nest, the child asked me: this is why? Do the old pigeons not want their own children? I don't know why, do any of you know that ?