Birds can thank dinosaurs for their colorful eggs

November 1, 2018, 1:11 p.m.
An assortment of paleognath and neognath bird eggs and a fossil theropod egg on the right.
Photo: Jasmina Wiemann/Yale University

Birds only use two pigments, red and blue, to create a dazzling array of colorful and speckled eggs. Scientists thought these colors evolved independently, meaning it was an avian innovation. But it turns out our beaked friends owe a colorful debt to non-avian dinosaurs.

According to a study published in Nature, birds' eggs are the result of dinosaurs that began to lay their eggs in open or partially open nests. The colors evolved as a result of this practice. (Many dinosaurs buried their eggs.) Once eggs were easier to see, they were more exposed to the elements, including egg-nabbing predators. Colors and speckles provided some camouflage and protection.

"This completely changes our understanding of how egg colors evolved," the study’s lead author, paleontologist Jasmina Wiemann, said in a statement released by Yale University. "For two centuries, ornithologists assumed that egg color appeared in modern birds’ eggs multiple times, independently."

To determine how birds got their colored eggs, researchers looked at 18 fossil dinosaur eggshell samples from all over the world. They used nondestructive laser microspectroscopy to test for red and blue pigments. They found these pigments in eggs belonging to oviraptors, relatives of the famed velociraptor, and other dinosaurs that are closer to birds on the evolutionary tree than, say, triceratops, whose eggs displayed no such evidence of coloring.

The photo above shows a collection of bird eggs next to a fossil theropod egg on the right. Theropods are a suborder of dinosaurs that birds evolved from.

"Colored eggs have been considered a unique bird characteristic for over a century. Like feathers and wishbones, we now know that egg color evolved in their dinosaur predecessors long before birds appeared," said Mark Norell, co-author and the Macaulay Curator of Paleontology at the American Museum of Natural History.

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