Ever Wondered Why Some Eggs are Different Colors?

Does It Matter Which Color Egg You Buy? (Why Are They Different?) | Egg Shell Color Science 

How Different Colored Eggs Are Formed, Why Some Eggs are Different Colors, Egg Shell Color pigment Science, interesting science behind brown egg white wgg blue green speckled egg
Why are chicken eggs different colors?

There’s a lot more science behind it than you might think.

Eggs come in a variety of colours – white, brown, blue, green, and speckled.

The difference in shell pigmentation is superficial, but the reasons are genetic and evolutionary, dating all the way back to dinosaurs.

Brown eggs

Let’s start with the familiar white and brown chicken eggs.

You might have a preference, but one doesn’t have more protein or a better taste than the other, though brown eggs tend to have slightly more Omega-3 fatty acids.

Brown eggs also come from larger chickens that cost more to maintain, which is why those eggs are a little more expensive.

It’s not because they’re way better.

Brown eggs get their color from a biochemical pigment called protoporphyrin formed by blood cells breaking down. And of course biochemical pigments are due to genetics.

White eggs

White-feathered chickens with white earlobes called Leghorn chickens lay white eggs while one type of red or brown chickens with red earlobes called Orpingtons lay brown eggs.

Blue Eggs

But, it gets weirder. The Ameraucana breed lays blue eggs, giving it the nickname of the Easter egg chicken.

Green Eggs

Olive Eggers, a cross between a hen and rooster that are from a brown egg and a blue egg laying breed, lays olive green eggs.


Science Behind the Egg Shell Pigmentation

How Different Colored Eggs Are Formed?

In each case, the pigment is deposited on the egg as it moves through the hen’s oviduct,fairly late in the shell-forming process – the last 3 to 6 hours of a 20 to 26 hour process. so the color doesn’t actually pass through the shell.

If you look at the inside of the shell of a brown egg after you crack it, the inside is white, not brown like the outside.

Brown eggs get their color from a biochemical pigment called protoporphyrin formed by blood cells breaking down. And of course biochemical pigments are due to genetics.

But aside from genetics, there are other factors that can influence an individual egg’s pigment.

Lighter Egg

A bigger egg would need more pigment to cover it, so if the hen only releases a set amount, that egg can be lighter. An older hen will generally lay lighter eggs.

The egg can rotate as it moves through the hen, too, meaning pigment can be unevenly distributed.

Stress on the hen can lead to less pigment and a lighter egg as well.

Blue color Egg

As for the more interesting colors we see, such as the blue eggs, the color comes from a pigment called oocyanin, a by-product of bile production.

But there’s an evolutionary advantage to blue eggs, since birds like robins and emus lay their eggs in an open nest. The blue pigment filters out UV light, protecting the egg from sunlight and stopping it from overheating.

The darker blue eggs are generally found in environments where there’s less direct sunlight; the darker pigment absorbs more sunlight to warm the egg.

Speckled eggs

Speckled eggs, meanwhile, have inherent protection from predators, offering a bit of camouflage while they sit in a nest.

Unpigmented Eggs

This explains why other egg-laying animals lay unpigmented eggs, like turtles. Turtles bury their eggs in a protected nest so don’t need the UV protection or camouflage.

This all has led scientist to conclude that egg colors came about around the time that species starting laying eggs in uncovered nests rather than bury them, something dinosaurs species like Ovirapt- like these were known to do.

So which ever eggs you choose to buy, you’re making an egg-cellent choice.


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