3D printing has been moving forward by leaps and bounds and now, scientists have used it to create something a bit unusual: artificial eggs. Researchers have printed the eggs in order to test how birds identify and reject the eggs that invading "brood parasites" sometimes sneak into their nests.
Brood parasites are birds that don't build nests of their own. Instead, they slip their eggs into the nests of other species. Then, the parents may raise the invading chicks at even the expense of their own. In some species, this has led to a sort of evolutionary arms race in which host parents get better and better at identifying and rejecting eggs while brood parasites have become more adept at mimicking the eggs of their host species.