There are about 18 species of penguins, and though their mating behaviors are "fundamentally similar," each species has its own quirks, said penguin researcher Emma Marks of the University of Auckland in New Zealand.
Breeding usually takes place during the Antarctic summer (October through February), though some species do mate in the winter. Males arrive at the colony first and choose their spot to wait for prospective mates. For nest-building penguins, such as Adélie penguins, males will go back to their previous nest and make it as presentable as possible, by building it up with stones, sticks and other objects they find.
When the females arrive, sometimes a few weeks later, they go right back to their mates from the previous year. A female will check out the quality of her old flame's nest by inspecting it, getting in it and lying down. She will do the same for neighboring nests, though this can sometimes lead to trouble. [In Photos: The Sex Habits of Penguins]
"If the male's previous partner arrives, she will kick the new female out of the nest," Marks told LiveScience. "It's a little bit like watching a soap opera."
For species that don't build nests (and even some that do), song quality is very important. Research suggests that females can tell how fat a male is — and thus how long he will be able to babysit the eggs without needing to run off in search of food — based on his song.
Once a female chooses her mate, the pair will go through an important courtship ritual, in which the penguins bow, preen and call to each other. The ritual helps the birds get to know one another, and learn their respective calls so that they can always find each other.
Courtship complete, the pair then mates. The female will lie down on the ground and the male will climb on her back and walk backward until he gets to her tail. The female will then lift her tail, allowing the penguins' cloaca (reproductive and waste orifice) to align and sperm to be transferred.
After the female lays one or two eggs, the male will take the first incubation shift. In species that don't build nests, the adults incubate by balancing the eggs on their feet. Incubation duties are shared between the parents in all species except one. In Emperor penguins, the male takes care of his egg for two months straight, relying on the warmth of his fellow penguin papas to survive the cold as his fat reserves dwindle.