After mating, a female Ostrich will lay 7 to 10 eggs at a time. The Ostrich lays the largest eggs, they weigh around 3 pounds and measure around 6 inches. Only dinosaurs had larger eggs than them. The incubation period is around 42 days. After hatching, the chicks will start leaving their nest with their parents only after a few days. By four months, they start showing their adult plumage; by six, they are about the size of a grown Ostrich. They reach their sexual maturity around 3 or 4 years old, which is when the males grow their black and white feathers.