Although this process can be observed during the year there are two presentations: December-January in the Southern Hemisphere and June-July in the Northern Hemisphere. This seasonality is due to the fact that birds born in June-July in the Southern Hemisphere and other birds born in December-January in the Northern Hemisphere start to put. The combination of an increase in the production of estrogens, the increase of energy of the food of layers and the reduction of the loss of energy, due to the increase of temperatures are the three causes of this seasonal process.