If this is not done, then the age difference between the oldest and youngest chick will be so great that the youngest generally has a poor start in life. It may go short of food because it is so small or it may get injured from its larger siblings stepping on it. The only alternatives are to either destroy the extra eggs or to remove the youngest chicks to handfed them and replace them to the nest when they are full. In this manner, they are not suffering nutritionally and will only have to avoid being trampled. After about ten days their eyes open and their feathers appear.
Growth is then rapid.
The difference between a chick at three weeks of age and one seven to ten days older is quite amazing. If all goes well the chicks will fledge around five to six weeks. They continue to be fed by the parents,usually the cock,for another week or two. By this time, the hen has usually started laying a second round of eggs. The danger period for the chicks is when they are about ten days old.