Preserved Egg
Eggs are freshest for up to two weeks, if people don't put them in a refrigerator, they can only be safely eaten for about two weeks before they become stink. We collected a huge amount of eggs in the late autumn, as well as different species of animals as the supplies of protein for the cold winter.
In this case, those birds' eggs won't be consumed in a short time and we need to process them before eating them during winter, or we might only have a mountain of stink eggs in the central cave. Fortunately, I know how to make preserved eggs according to a traditional Chinese recipe: the chemistry reactions are similar to those when making ancient organism soaps — using alkali to break down some of the fats in the eggs and make them have longer preservation time.