How big gray swallows can have eggs

Gray Yan can give birth to eggs more than one year old.After this bird enters the breeding period, we must first estrus it. After finding the right opposite sex, the pairing will be completed and preparing to build the nest.After the nest is built, the female birds will start laying their eggs. Usually a nest will produce 4-7 eggs, and after 13 days of incubation, the chicks will break out of the shell.Birds will feed the young birds until its feathers are full and leave the nest.