Penguin fathers are very hands-on when it comes to taking care of their young. For weeks, male penguins take egg-sitting duties while the mother heads to sea to search fish for her soon-to-hatch offspring. During this time period, males fast, but if the chick hatches before the mother penguin returns, the father can still produce a curd-like substance, which he regurgitates to keep baby fed.
In fact, males are so important to this brooding process that females seek out partners who can sit on eggs longer without food. One study in 2010 found that females can tell how fat a male penguin is by listening to his hoarse mating cries.