The Glossiness of Tinamou Eggs

Eggs from tinamous being used for research at Hunter College. Tinamou eggs are up to 14 times as glossy as the average chicken egg. Credit Fred R. Conrad/The New York Times

Readers of the blog who have visited in recent months will know that I do a lot of work with chicken eggs for artistic purposes, and readers from years ago might remember that I worked with Celebrate Urban Birds at the Cornell Lab of Ornithology, and I often wrote about bird-related topics (and still do!). During one of CUBs’ photo competitions called Funky Nests, I posted on egg coloration, and looking back on that post I am very surprised to see that I didn’t mention the eggs of a family of birds called tinamous. I’m puzzled as to why I wouldn’t have written about tinamou eggs because they are curiously glossy. In addition to having quite pretty colors, the eggs are extremely shiny to the point of looking fake, or varnished by wood elves after they’re laid.

Perhaps I didn’t include tinamou eggs in my post because very little is understood about why their glossiness exists, as Rachel Nuwer reports for the New York Times this week in an article with a title that obviously caught my eye:

Easter Eggs Without a Kit

The Shy, Drab Tinamou Has a Stunning Palette That Still Holds More Mysteries Than Answers.

When it comes to shell color, most birds’ eggs conform to one of four motifs: colored with spots, colored without spots, white with spots or pure white.

But there is a striking exception: the eggs of the tinamou, a shy, ground-dwelling bird native to South and Central America. Tinamous, which look something like a cross between a guinea hen and a roadrunner, blend in with their forest environment by sporting drab plumage in shades of brown and gray. But they produce some of the most spectacular eggshells in the world, in colors like sky blue, lime green and rich chocolate and so glossy that they can reflect overhead trees and brush.

Now a study in The Journal of the Royal Society Interface takes a close look at the tinamou eggs and finds that they possess a unique structure and iridescence — the only known example ever found in eggshells. “Working with these eggs was, for me, like becoming an artist,” said Mark E. Hauber, an animal behaviorist at Hunter College and author of The Book of Eggs. “They are so unique and unusual that it was hard to take my eyes off them.”

To crack the structural secrets of the eggs’ ceramic appearance, Dr. Hauber and his colleagues first obtained green, blue, light brown and dark brown eggs from four species of tinamou kept by the Bronx Zoo, the Dallas World Aquarium and a private breeder.

You can read the full original article here, or on page D2 of the New York December 23, 2014 edition of the Times.

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