The Color of Eggs, Part III

As you can see from the photo, our Araucanas have begun laying their blue eggs. You may remember from our earlier post that most of our chickens did not begin laying until I explained fried chicken to them. That did not work on the Araucanas and it wasn’t until this week that I figured out why: Araucanas are from Peru and don’t speak English. I don’t speak Quecha but fortunately both the chickens and I could communicate in Spanish. Can you say “fried chicken” in Spanish?

Which brings us to Part III of our series on the color of bird eggs. As we mentioned at the end of our last post in the series, scientists are not inclined to give credit to female avian artistry and look for scientific explanations of why birds go to the trouble of coloring their eggs. They don’t accept our “art hypothesis.”

Their answer is adaptation. The theory goes like this: To survive, bird eggs must protect the small birds inside until they can peck their way out. If egg-eating predators have an easy time finding the eggs, it is much less likely that little birds will live to hatch and then reproduce the species. After all, skunks don’t care whether the egg they eat today means no eggs for their grandchildren. (Or we assume they don’t.)

Like lawyers adducing evidence at trial, the scientists bring forth first, Exhibit A: the Killdeer, which lays eggs in the open. Such eggs would be easy sightings for visual predators unless well camouflaged, as Killdeer eggs are. Coupled with the small similarly marked and colored rocks which Killdeer frequently use to line their nests, the entire apparatus is practically invisible which obviously aids in Killdeer survival. (Killdeer are experts at distraction displays which we discussed briefly in our post about Rikki-tikki-tavi. They are ground nesters.)

Exhibit B consists of white eggs laid by birds which nest in dark holes such as Petrels, Woodpeckers, Kingfishers. White eggs are easier to see in the dark. Exhibit C brings more white eggs, this time of species which leave nests frequently but cover the eggs with grasses or other plants in the vicinity before leaving which hides the eggs from flying eyes.

But there is a hole in this theory and it is the White Leghorn hen, that prolific egg layer we and E.B. White talked about in the first post on egg color. The one who would stop to lay an egg even if she was on the way to a fire. If the purpose of egg color is camouflage to conceal the eggs from predators, who is in more need of that than a domestic chicken whose every egg is stolen from her by two legged mammals? Why does she lay white eggs visible for miles?  I think the scientists have a little way to go to finish their explanation. Given what we are learning about bird brains and how evolved they really are, perhaps scientists should take another look at our art hypothesis.

But I can hear them now, “It isn’t just chickens and birds that hide their eggs when they leave their nests who lay white eggs. Exhibit D contains the eggs of Hawks and Owls and other birds which begin incubating their eggs as soon as the first one hatches. No need to camouflage those because the parent is sitting on them.”

We’ll let you know the verdict when it comes in.