Emperor Penguin Dads
Emperor penguins have a breeding cycle unlike any other penguin species. Their 9 to 10 month cycle requires that breeding begin in April or May, which is the austral autumn when most penguins are migrating. Emperors are also unique because only the male incubates the egg. Upon laying the egg, the female passes it to the male and heads to the sea to travel to distant feeding grounds. The male is left to face the Antarctic winter, carrying the egg on his feet for 15 weeks or more and losing half his body weight in the process. By packing in a tight group, males reduce the surface area of their body that is exposed to the wind. They continually shift positions so that each bird spends equal time inside and outside the group. If the chick hatches before the female returns, the male can even produce milk by breaking down its body tissues to sustain the chick until its first feeding. When the female returns, the male hurries to the sea to nourish himself and collect food for his hungry offspring.

Extra Eggs for Crested Penguins
All penguin species, except the King and Emperor, lay two eggs, which are roughly the same size and shape. The six species of crested penguin however, lay two eggs, but only rear one chick. The first egg is 15-40% smaller than the second one, with the size difference between the two eggs the largest for any bird. Even though the second egg is laid about six days following the first, it hatches first. The eggs of the Fiordland, Snares, and Rockhopper penguins both hatch, but the smaller chick from the late-hatching first egg cannot compete with its sibling and dies of starvation. On the other hand, the Erect-crested, Royal, and Macaroni penguins lose their first egg before the second egg is laid. In fact, in Royal penguins, if the first egg is not crushed or punctured early in the nesting season, the egg is kicked out of the nest shortly after the second egg is laid.

Why do these penguins bother laying two eggs if they only raise one chick? The first egg may serve as a back-up in case the larger egg is lost or destroyed. Another theory is that crested penguins may be slowly reducing their clutch size to one egg, like that of King and Emperor penguins. For now, the reason for egg size differences is unknown.

Penguin Pairing
Although penguins do not mate for life, roughly 60-90% of female penguins select the same mate they had in a previous breeding season upon arriving at the breeding grounds. In Macaroni penguins, 80% of pairs stay together for at least four successive breeding seasons and Yellow-eyed penguins have been observed to stay together for as long as 13 years. Only 29% of Kings and 15% of Emperor penguins pair with their old breeding partner, however. This is probably because these species spend less time together at the breeding grounds than other species.

Pesky Pests
Like any bird, preening is an important task for penguins to keep their feathers in top condition and remove parasties. Equitorial penguin species engage in mutual preening, as they are often heavily infested with fleas and ticks. Most ticks die when penguins enter the water, but when moulting or incubating eggs, ticks are a major problem for penguins, especially those that nest in forest cover. Penguins that live in cold regions however, like Emperors, Kings, Adelies, Gentoos, and Chinstraps, have no pests to worry about because no insects can survive in the cold Antarctic climate.