Being members of the bird family, penguins do lay eggs when reproducing. Depending on the species of penguin, the incubation process takes anywhere from 1 to 2 months. The larger emperor penguin eggs take longer to incubate.
Once the female lays the eggs, she leaves to replenish her health while the father incubates the eggs. After that point, the two take turns warming the eggs, giving the other penguin parent a chance to feed for days at a time. This is not the case with emperor penguins, however. With this species, the male incubates the eggs for nearly the entire hatching period.