Why Do Birds Have Colorful Eggs? Because They’re Dinosaurs

  • Why Do Birds Have Colorful Eggs? Because They’re Dinosaurs

Why Do Birds Have Colorful Eggs? Because They’re Dinosaurs

According to researchers at Yale, the American Museum of Natural History, and the University of Bonn, birds inherited their egg color from non-avian dinosaur ancestors that laid eggs in fully or partially open nests.

Birds evolved from eumaniraptoran dinos in the Jurassic Period consist of Archaeopteryx, the earliest-known bird that lived about 150 million years ago in Germany. Eggshell theories were "kind of all over the place", said study author Mark Norell, a paleontologist at the American Museum of Natural History in NY. Researchers found that birds' close dinosaur relatives had eggs with traces of two pigments-a red-brown one and a blue-green one.

Egg colors of archosaurs: the internal nodes are (1) Archosauria, (2) Dinosauria, (3) Ornithischia, (4) Saurischia, (5) Eumaniraptora, (6) Paraves and (7) Aves; the egg icon in the phylogeny labels Eumaniraptora. However, many theropod dinosaurs, which walked on their hind legs and are thought to be the direct ancestors of modern birds, did indeed have color patterns as well as speckles and spots on their eggs. Instead of using the chemical analysis they developed for the 2017 study, which required grinding up fossil specimens, they turned to an innovative technique for studying fossils: something called Raman microspectroscopy.

If you're interested in all the practical advantages of speckled and brightly colored eggs, check out this article.

The evolutionary link between dinosaurs and birds has been recognized for centuries but ornithologists long believed that birds evolved their colored eggs several times over history, mimicking local hues to help their eggs blend in.

Darla Zelenitsky, a dinosaur paleontologist at the University of Calgary, said the combination of new technology and the method that Wiemann and Norell worked on allowed them to show "that there was a single evolutionary origin of egg color".

Though most of us are familiar with blue-speckled robin's eggs or golden-brown chicken eggs, the sheer range of colors and patterns on bird eggs is wonderful: they can be brick-red, marbled in patterns that look like the surface of the Moon, or covered in squiggly lines like a Jackson Pollock painting.

Bird eggs can be amazingly colorful, everything from robin's egg blue to green, even red. Stem birds, she said, were on the way toward what is considered modern birds and had "mixed characteristics", like teeth.

"Birds were not the first [egg-layers] to produce coloured eggs", the researchers write. Birds with white eggs today, such as ostriches, parrots, and some domestic chickens, must have later lost the trait of coloring their eggs through evolution, she says.

More specifically, Wiemann thinks egg color evolved when certain dinosaurs started building open nests, rather than burying their eggs. They discovered that some branches of the dinosaur tree had no pigment on their eggs, including sauropods and many other large, four-legged species. Given the analytical methods from other scientific disciplines now available for work on fossils, "It's an incredible time to be a paleontologist", she says.