Charles Darwin himself treasured a tinamou egg from a different species. The egg was found after Darwin's death in his collections. At some point during his lifetime, Darwin accidentally cracked the egg, but the still-shiny specimen went on display earlier this year.
For the new study, Igic, a researcher from the University of Akron's Department of Biology and Integrated Bioscience Program, and the other researchers used chemical analysis and a barrage of high-powered magnifying devices to study tinamou eggs.
They determined that an extremely smooth cuticle produces the glossy appearance of tinamou eggshells. The cuticle is composed of calcium carbonate, calcium phosphate and, potentially, organic compounds such as proteins and pigments.
How does it change color? Not all color is pigment-based. A crystal, for example, may look rainbow colored from certain angles even though it is clear, simply because of the way it reflects light. Some insect bodies and bird feathers also exhibit radiant colors due to how their structures impact light.