Emperor penguins lay in the Antarctic autumn, on sea ice rather than bare ground. The female transfers her single egg to the male's feet, where it sits beneath a brood pouch, and then walks back to open water to feed. The male incubates for roughly two months through the polar winter, fasting the entire time.
Survival depends on huddling. Thousands of males pack together and the group slowly rotates, so that birds on the windward edge cycle inward. Temperatures inside a huddle can rise far above ambient. Over the whole fasting period, which includes the courtship weeks before laying, a male may go without food for something on the order of four months and lose a substantial share of his mass.
The common misreading is that this is chivalry. It is scheduling. Winter incubation means the chick fledges in summer when food is nearest and the ice is breaking up, and the sexes simply alternate long foraging trips. The real vulnerability is that the whole arrangement depends on fast ice staying put until the chicks have fledged.